Kidney cancer usually refers to renal cell carcinoma. A significant number of large kidney cancers can be asymptomatic. Kidney cancer without any symptoms is called incidental kidney cancer. Such patients are often unintentionally found the kidney mass by ultrasound examination of physical examination. Some patients come to the clinic with blood in urine or increased red blood cells in urine test, back pain, fatigue, low fever and swelling of lower limbs. There is no specific blood test for kidney cancer. Imaging examination plays a very important role in the diagnosis of kidney cancer. Definitive diagnosis relies on pathological examination. 1. Abdominal ultrasound or color Doppler ultrasound Most kidney tumors are first detected by ultrasound. About 80% of incidental kidney cancers are first detected by ultrasound. However, generally speaking, it is difficult to detect kidney tumors less than 1.5cm in diameter by ultrasound. 2. Abdominal CT scan and enhancement scan This test is currently the gold standard for the diagnosis of kidney cancer. At present, about 90% of kidney cancer is diagnosed by CT scan + enhancement of upper abdomen, and CT is useful to judge the stage of tumor before operation. 3. Magnetic resonance examination MRI has the same value as CT in the diagnosis of kidney cancer, but it is usually used to evaluate the presence and location of renal vein vena cava cancer thrombosis. The latest study shows that MRI has a certain role in determining the pathological type and stage of kidney cancer. 4. Abdominal ultrasonography is currently mainly used in the diagnosis of patients with iodine allergy and renal function impairment of kidney tumor. Furthermore, it has clinical value for the diagnosis of cystic kidney cancer. 5. Puncture biopsy of renal tumor For renal tumor preoperative puncture biopsy of renal tumor is not recommended at present. For those who have difficulty in definite diagnosis or advanced renal tumor requiring targeted therapy, puncture biopsy can be considered. The above tests are very important for the diagnosis and differential diagnosis of kidney cancer, but not all of them are required. However, not all of them are necessary, and the specific items need to be done according to each patient’s specific situation. Most of the patients can be diagnosed through the above tests.