To determine the incidence of DVT and to evaluate the risk factors of DVT under LMWH prophylaxis in patients with thoracolumbar fractures caused by high‑energy injuries postoperatively. A total of 534 patients from January 2016 to November 2019 were included in this retrospective study. Medical record data, including demographic data, perioperative variables, and laboratory results, were collected. LMWH prophylaxis was used for DVT in all the patients. The incidence and risk factors of DVT after surgery were identified by logistic regression analysis and receiver operating characteristic (ROC) curve analysis. The overall incidence of postoperative DVT was 18.91% (101/534). Three patients (0.56%) had proximal DVT and ninety-eight (18.35%) patients had distal DVT. The incidence of postoperative DVT in patients with thoracic fractures was 26.80% and 15.50% with lumbar fractures. The multivariate analysis showed that six risk factors increased the incidence of postoperative DVT, including advanced age, decreased lower extremity motor, blood transfusion, duration of bed rests, fibrinogen (FIB), and D-dimer. The ROC analysis indicated that the diagnostic value of D-dimer was highest whose area under the ROC curves (AUC) value was 0.754. Despite LMWH prophylaxis, the risk of postoperative DVT is still very high, especially in thoracic fracture. Advanced age, decreased lower extremity motor, blood transfusion, duration of bed rests, FIB, and D-dimer are risk factors for DVT. Moreover, the diagnostic value of D-dimer is the highest among these factors.