Renal cancer venous thrombus is not necessarily a cancerous thrombus. Kidney cancer is a collective term for malignant tumors occurring in the kidneys, which contains primary kidney cancer and secondary kidney cancer. Primary renal cancer is the most common and is a malignant tumor originating from the epithelial system of the renal tubules, whereas clear cell carcinoma accounts for the majority of them, about 85% of renal malignant tumors. Kidney cancer cells can metastasize/invade into the renal veins causing cancerous blood clots, which are part of the progression of the disease and can lead to poor blood flow. Renal cancer vein thrombosis often has a great impact on the survival period and the quality of survival of patients, once found, it needs to be treated promptly, if it can be treated surgically, try to undergo surgery as early as possible, but most of the patients are not able to undergo surgical treatment, such as targeted therapy, so that the cancerous thrombus can be subsided and reduced in size. In addition, some patients may have thrombus formed by coagulation of blood components, which is not cancerous thrombus at this time. Kidney cancer venous thrombus must actively cooperate with doctors to take treatment to control the condition and prolong the survival period.