Objective: To investigate the clinical features and management of deep venous thrombosis (DVT) in patients with malignant tumor. Methods: The clinical data of 45 patients with malignant tumor and complicated by DVT were reviewed to summarize and analyze the causes, prevention and treatment methods of thrombosis of these patients. Results: Of the patients, the clinical symptoms in 38 cases (84.4%) were improved after standard anticoagulation/thrombolytic treatment, and one of them developed subcutaneous ecchymosis; four cases (8.9%) developed pulmonary embolism (PE) during anticoagulation/thrombolytic therapy, of whom 3 cases had their PE symptoms relieved after aggressive treatment, and 1 cases died despite lifesaving efforts; the symptoms of 3 cases (6.7%) with risk of bleeding were relieved only by immobilization, symptomatic treatments and blood circulation promoting drugs. In the 8 patients with peripherally inserted central venous catheter (PICC)-related upper extremity DVT, the catheters were removed after treatment according to individual situations, and no obvious PE symptoms were noted. Conclusion: Patients with malignant tumor have a higher risk of DVT and aggressive treatment should be initiated as early as possible after the diagnosis of DVT in these patients. For patients with DVT without apparent predisposing cause should receive high vigilance for the possibility of to occult malignant tumor.