Kidney is an important organ of the human body, and the level of renal function gradually decreases in the vast majority of people as they grow older. Some studies show that glomerular filtration rate (GFR) decreases by 0.75 ml/min per year in about 1/3 of patients. moreover, a variety of diseases can lead to renal insufficiency in patients, such as nephritis, hypertensive nephropathy, and diabetic nephropathy. When clinically treating tumor patients with combined renal insufficiency, we have to consider two aspects. On the one hand, what is the effect of renal insufficiency on anti-tumor treatment, and on the other hand, whether anti-tumor treatment will aggravate renal function damage of patients. First of all, we know that kidney is the organ for metabolism and excretion of many kinds of chemotherapeutic drugs and their metabolites. When patients have renal insufficiency, the secretion, metabolism and distribution of the drugs used will be affected, and the highest blood concentration of the drugs will be increased, and the excretion will be delayed, which will be manifested as the increase of the toxic reaction of the patients after the use of the drugs. So we need to fully understand the patient’s renal function status before treatment. Blood creatinine (SCr) is a common indicator used in clinical evaluation of patients’ renal function. However, this index is affected by the patient’s own muscle volume, and the creatinine level of the patient increases when the muscle volume is large. Moreover, in the early stage of renal function damage, the change of SCr level is not obvious, which cannot accurately reflect the degree of renal function damage in the early stage. Therefore, the glomerular filtration rate is commonly used to illustrate the renal function of patients in clinical practice. Glomerular filtration rate (GFR) represents the filtration function of all glomeruli in the kidney, and a decrease in GFR represents impaired renal function, which is generally 70-100 ml/min. Creatinine clearance can be calculated by measuring the creatinine excreted in the urine of a patient over a 24-hour period, which is used to represent the patient’s GFR. This method is affected by the patient’s diet, and it may overestimate the patient’s renal function due to the secretion of creatinine by the renal tubules. This method is influenced by the patient’s diet and may overestimate the patient’s renal function due to tubular creatinine production. Another simpler method is the empirical formula method, in which the patient’s GFR is estimated from Scr, patient’s age, body weight and other factors by empirical formulas, and the parallelism between the GFR calculated by this method and the patient’s actual GFR is better, and the Cockcroft-Gault and MDRD formulas are commonly used in the clinic at present. On the other hand, the impact of tumor and tumor diagnosis and treatment on renal function is multifaceted. Tumors themselves have an impact on renal function and can lead to pre-renal, renal and post-renal problems. Pre-renal disease mainly refers to the patient’s low blood volume and low blood pressure, which leads to hypoperfusion of the kidneys and thus renal function impairment. Renal factors are multifaceted and can be glomerular, tubular or interstitial diseases, vascular lesions, or result from direct infiltration of the kidney by a tumor. Glomerular diseases include membranous nephropathy, microscopic lesions or focal glomerulosclerosis, amyloidosis, and proliferative glomerulonephritis. Postrenal factors refer to urinary tract obstructive lesions caused by tumor or metastatic foci compression and invasion of the urinary tract. If bilateral urinary tract obstruction occurs, it may lead to renal failure. Some other tumors may cause fluid and electrolyte imbalance in patients, which can manifest as hyponatremia, polyuria, and hyperkalemia. During the tumor diagnosis and treatment, the examination measures as well as the drugs used for treatment may have an impact on the patient’s renal function. CT examination of tumor patients inevitably requires the application of iodine-containing contrast agents, and some patients with elevated creatinine develop contrast nephropathy after the examination. Other risk factors for contrast nephropathy are: Patients with previous renal impairment, blood creatinine more than 1.5mg/dL or GFR less than 60ml/min. Diabetic nephropathy. Patients with multiple myeloma. Severe cardiac failure or other causes of reduced renal perfusion. Coronary angiography. High dose application of contrast media. Types of contrast media: The first generation of contrast media was ionic and hypertonic. The second generation is nonionic and has a lower osmolality than the first generation, but is still hypertonic. The newest contrast agents are isotonic. The first generation of contrast agents had a higher likelihood of causing renal impairment in patients, whereas the newer isotonic ones have reduced nephrotoxicity. A variety of antitumor agents may cause renal dysfunction. The effects of antineoplastic therapeutic agents on renal function are multifaceted and can affect glomerular, tubular, interstitial, and renal microperfusion, with a variety of clinical manifestations that can range from asymptomatic elevated creatinine levels to acute renal failure requiring hemodialysis. Some drug-induced GFR decreases are dose-related and clinically predictable, and there are some drugs that cause renal damage that is irreversible in the long term. One of the representative drugs is cisplatin, which is the most common drug causing renal damage and the most nephrotoxic drug, and patients are generally required to have a GFR of 50-60 ml/min or more to be treated with cisplatin. And the following factors during antitumor therapy will further increase the risk of renal dysfunction in patients: Decrease in intravascular blood volume, which can be caused by a variety of reasons such as insufficient intake, vomiting, diarrhea, or pleural and abdominal fluids, is the most common factor inducing renal impairment with antitumor drugs. Other nephrotoxic drugs applied concurrently with chemotherapy, such as aminoglycoside antibiotics, nonsteroidal anti-inflammatory drugs, and some traditional Chinese medicines, or the patient’s imaging with iodine-containing contrast agents, may further aggravate the patient’s renal dysfunction. The patient has concurrent urinary tract obstruction. Therefore, for tumor patients with renal insufficiency, we have to accurately assess the renal function of the patients, while fully understanding the metabolic process of various drugs and their effects on renal function, selecting drugs according to the glomerular filtration rate (GFR) of the patients, and adjusting the dosage of the drugs in combination with the adverse reactions manifested by the patients clinically. At the same time, to prevent different reactions to drugs, to avoid risk factors that aggravate renal function damage, to ensure the patient’s blood volume, to avoid combining other nephrotoxic drugs, to release the urinary system obstruction, should try to choose drugs that do not cause renal function damage.