Patients with malignant tumor are easy to be complicated with venous thrombosis,which is the second leading cause of death for patients with malignant tumor.The mechanism of tumor thrombus forma-tion is related to tumor type,treatment,metastasis,heredity and tumor itself.Evaluating the risk of venous thrombosis in patients with cancer and providing targeted preventive anticoagulation measures for high-risk patients have important significances for improving the quality of life and prolonging the survival period of pa-tients with cancer.