Objective To assess the risk factors of postphlebitic syndrome(PS)after deep vein thrombosis of the lower extremities. Method In this study,102 DVT patients managed by conservative therapy were recruited.Data including age,sex,etiopathogenesis,anticoagulation,pathogenesis, elasticstocking therapy,degree of lower extremity exercise,INR,WBC,PT%and FIB were analyzed by single factor analysis and COX analysis. Result PS developed in 67.60%cases,single factor analysis shows:sex(P=0.025),anticoagulation(P=0.000),elastic-stocking therapy(P=0.000),degree of lower extremity exercises(P=0.000),INR(P=0.033),WBC(P=0.012),PT%(P=0.000),FIB(P=0.002)are related to the occurrence of PS.COX regression shows that anticoagulation(P=0.011),the degree of lower extremity exercise(P=0.019),elastic-stocking therapy(P=0.000)are related to PS.Age (P=0.299),etiopathogenisis(P=0.838)and pathogenesis(P=0.2 17)are not statistically PS related.Conclusion DVT is a multi-factors related disease.Multivariant analysis revealed that elastic-stocking (P=0.000),anticoagulation(P=0.011)and the degree of lower extremity exercises(P=0.019)are related to the development of PS.