Objective  To investigate the incidence of pre- and post-operative lower extremity deep venous thrombosis (DVT) in hospitalized patients with intertrochanteric fractures and to analyze the relevant risk factors.  Methods  A retrospective casecontrol study was conducted to analyze the data of 218 patients with femoral intertrochanteric fractures admitted to Xian Honghui Hospital, Xian Jiaotong University from July 2015 to October 2017, including 85 males and 133 females. There were 85 males and 133 females, aged 32-102 years ［(76.0±11.9)years］. Of the patients, 213 had open reduction and internal fixation, 4 partial hip arthroplasty, and 1 external fixation. All patients underwent deep venous ultrasound of the lower extremities before and after surgery to determine the occurrence of DVT. DVT of the lower extremities was divided into distal thrombosis, proximal thrombosis and mixed thrombosis. According to the preoperative and postoperative ultrasonography results, the patients were divided into thrombosis group ［82 patients (37.6%) before operation, 128 patients (58.7%) after operation］ and nonthrombosis group ［136 patients (62.4%) before operation, 90 patients (41.3%) after operation］. Location of DVT were recorded before and after operation and outcome was evaluated. All patients were assessed for risk factors associated with thrombosis, including general patient data, time of surgery, tourniquet time, blood transfusion, blood loss, fluid volume, drainage, and serological markers. Multivariate Logistic regression analysis was used for detecting the risk factors.  Results  The DVT rate was 37.6% preoperatively and increased to 58.7% postoperatively. The type of thrombosis was mainly distal DVT, which accounted for 86.6% and 90.6% of DVT before and after surgery, respectively. After the operation, 2.8% of the distal DVT extended above the popliteal vein. A total of 23.4% of the patients had no thrombosis before surgery, and distal, proximal, or mixed DVT occurred after surgery (22.0%, 0.5% and 0.9%, respectively). No fatal pulmonary embolism occurred. The univariate analysis showed no statistical differences between the preoperative thrombosis group and nonthrombosis group in terms of age, gender, fracture side, combined diseases, body mass index, American Society of Anesthesiologists (ASA) classification, admission D-dimer, and admission C-reactive protein (CRP) (P＞0.05), but the time from fracture to hospitalization and the time from fracture to surgery were significantly different between the two groups (P＜0.05). There were no statistical differences between the postoperative thrombosis group and the postoperative non-thrombosis group in age, gender, fracture side, combined diseases, body mass index, length of stay, ASA classification, surgical method, operation time, blood transfusion, blood loss, infusion volume, drainage volume, D-dimer on admission, and CRP on admission (P>0.05), but the time from fracture to admission, time from fracture to surgery, D-dimer before surgery, D-dimer at day 1 after surgery, D-dimer at day 5 after surgery, and CRP at day 5 after surgery showed significant differences between the two groups (P<0.05). Multivariate analysis results showed the time from fracture to hospitalization (OR=1.109, 95%CI 1.003-1.225, P<0.05) and the time from fracture to surgery (OR=1.090, 95% CI 1.007-1.180, P<0.05) were independent risk factors for preoperative DVT. The time from fracture to hospital (OR=1.137, 95% CI 1.002-1.290, P<0.05) and 1 day postoperative D-dimer (OR=1.087, 95% CI 1.033-1.142, P<0.05) were independent risk factors for postoperative DVT.   Conclusions  For intertrochanteric fractures, distal DVT is the main type of thrombosis.  Time from fracture to hospitalization is an independent risk factor of DVT before and after operation, and time from fracture to operation is an independent risk factor of DVT before operation. Early intervention (early admission and early surgery) may reduce the incidence of DVT.