Objective:To investigate the risk factors associated with post-thrombotic syndrome (PTS) within 2 years after the first diagnosis of deep venous thrombosis (DVT) of the lower extremities.Methods:The clinical data and 2-year follow-up data of 260 patients who were first diagnosed with DVT at our department from Jan 2017 to May 2019 were retrospectively analyzed.By Villalta score, the patients were divided into non-PTS group, mild PTS group and moderate-severe PTS group. Ordered multiple classification logistic regression was used to analyze the risk factors for the development of PTS.Results:The incidence of mild and moderate-severe PTS was 22.7% and 15.8%, respectively. Multivariate Logistic regression analysis showed that recurrence history of DVT ( OR=4.754, 95% CI 1.84-12.01, P=0.001), duration of oral anticoagulation treatment ≤6 months (0-3 months: OR=7.791, 95% CI 1.79-33.90, P=0.006; 4-6 months: OR=4.242, 95% CI 1.13-15.99, P=0.033), time length of stretch sock wearing≤ 12 months (0-6 months: OR=9.708, 95% CI 1.81-52.14, P=0.008; 7-12 months: OR=4.899, 95% CI 1.42-16.88, P=0.012) and exercise frequency ≤4 times/week (1-2 times/week: OR=7.691, 95% CI 1.92-30.72, P=0.004; 3-4 times/week: OR=4.284, 95% CI 1.33-13.80, P=0.015) were risk factors for PTS. Catheterized thrombolytic therapy ( OR=0.436, 95% CI 0.20-0.96, P=0.039) and low body mass index (BMI<18.5 kg/m 2: OR=0.142, 95% CI 0.02-0.81, P=0.028), central thrombus ( OR=0.322, 95% CI 0.15-0.72, P=0.005) and peripheral thrombus ( OR=0.020, 95% CI 0.01-0.07, P<0.001) were protective factors for PTS. Conclusions:Patients with DVT have a high risk of developing PTS within 2 years. Catheter-directed thrombolysis, no history of recurrence of DVT, low BMI (<18.5 kg/m 2), central or peripheral thrombosis, long-term oral anticoagulant therapy (≥7 months), longer wearing time of elastic socks (≥1 year), and higher exercise frequency (≥ 5-6 times/week) can be conducive to the reduction of incidence and severity of PTS.