Objective:To investigate the mechanism of methyltetrahydrofolate reductase ( MTHFR) C677T polymorphism in the pathogenesis of lower extremity deep vein thrombosis (DVT). Methods:Used retrospective controlled study method, a total of 64 DVT patients (DVT group) and 96 healthy people (control group) were enrolled in the Affiliated Hospital of Traditional Chinese Medicine, Xinjiang Medical University from August 2019 to August 2021. Clinical manifestations and related detection, including D-dimer, fibrinogen, prothrombin time, prothrombin activity and prothrombin time-international normalized ratio of the subjects were recorded, and plasma homocysteine (Hcy) and soluble endothelial cell protein C receptor (sEPCR) were detected by enzyme linked immunosorbent assay (ELISA). The polymorphism of C677T locus of MTHFR gene was detected by polymerase chain reaction-restricted fragment length polymor-phism (PCR-RFLP), and the differences of blood indexes and MTHFR genotypes between the two groups were compared. Measurement data with normal distribution were represented as mean ± standard deviation ( ± s), and comprison between groups was conducted using the t-test; the skewness data were expressed by M( Q1, Q3), and rank-sum test was used for inter-group comparison. comprison between groups of count data was conducted using the chi-square test or Fisher exact probability. Results:Compared with the control group, DVT group showed more symptoms of limb skin redness, limb swelling, skin temperature rise, local tenderness, skin rupture, skin tension, pigmentation, limb movement and sensory disturbance, the difference were statistically significant ( P<0.05); the prothrombin time-international normalized ratio [0.98(0.95, 1.04) vs 1.05(1.00, 1.13)], fibrinogen [2.76(2.31, 3.30) mg/L vs 3.36(2.74, 4.35) mg/L], D-dimer [0.52(0.38, 0.62) mg/L vs 4.73(2.44, 12.05) mg/L], Hcy[(1 639.03±390.29)ng/mL vs (2 423.03±631.95) ng/mL] and sEPCR [(108.62±25.07) ng/mL vs (137.79±26.23) ng/mL] in DVT group were significantly higher than those in control group, the difference were statistically significant ( P<0.05); the prothrombin activity [90.70% (75.80%, 100.00%) vs 103.00%(93.00%, 112.50%)] was significantly lower than that of the control group, the difference was statistically significant ( P<0.05). Compared with the control group, CC, CT, TT genotype frequency and allele frequency of MTHFR C677T site in DVT group showed a trend of change, but the difference were not statistically significant ( P>0.05). Conclusion:TT mutation at MTHFR C677T site in patients with DVT has an increasing trend, which may promote the expression level of Hcy, and high expression of Hcy and sEPCR can induce the occurrence and development of DVT.