Objective To study the incidence and risk factors of deep vein thrombosis (DVT) in patients with low-extremity trauma and its relation with plasma D-Dimer. Methods We retrospectively analyzed 260 patients with low-extremity fracture. A serial color flow duplex scan was applied preoperatively to determining the presence of DVT, the incidence of DVT was analyzed, and the patients were divided into four groups, based on whether for DVT、the times of immobilization、gender and age, then D-Dimer was analyzed statistically. Results The overall incidence of DVT was 12.3%, among these,fracture of hip was highest(28.57%), fracture of foot and ankle was lowest(1.54%). Plasma D-Dimer level was higher in patients with DVT [(1527±373) μg/L] than those without DVT [(552±262) μg/L], (P<0.05). Conclusion The overall incidence of DVT was 12.3%. Higher age, higher energetic injury, more than 7 days immobilization and smoking were risk factors. Normal plasma D-Dimer concentration has important value of exclusion of DVT, and plasma D-Dimer level is affected by the high energy of injury and the time of immobilization.