[Objective] To explore the anatomical distribution characteristics of thrombosis after primary total knee arthroplasty, and to further explore the risk factors of proximal deep venous thrombosis. [Method] According to the inclusion and exclusion criteria, the clinical data of 97 patients admitted to our hospital from January 2016 to December 2018 were retrospectively analyzed. According to the site of postoperative thrombosis, there were 82 cases of distal type and 15 cases of proximal type. The sites of thrombosis were observed and compared between the two groups, and univariate and multivariate logistic regression analysis was used to further explore the related factors of proximal lower limb deep vein thrombosis. [Results] The most common thrombosis after total knee replacement involved the muscular vein, posterior tibial vein, fibular vein and popliteal vein. The incidence of isolated thrombus was higher in the distal type than in the non-isolated type (60 vs 22, 73.17% vs 26.83%), while the incidence of non-isolated thrombus was higher in the proximal type than in the isolated type (9 vs 6, 60% vs 40%). Univariate comparison showed that the operative time and duration of anesthesia in patients with proximal type were significantly higher than those with distal type (P < 0.05), and the ratio of preoperative varicose vein history was significantly higher than that in patients with distal type (P < 0.05). Multivariate logistic review showed that prolonged operative time (OR=1.111, 95%CI = 1.011-1.220, P=0.028) was a risk factor for proximal deep vein thrombosis after total knee arthroplasty. [Conclusion] Intermuscular vein thrombosis was the most common type of thrombosis after total knee replacement. Proximal thrombus was mostly non-isolated and distal thrombus was mostly isolated. In addition, prolonged operative time is a risk factor for proximal deep venous thrombosis.