Objective：To investigate the effect of continuous femoral nerve block on the deep vein thrombosis（DVT） in patients under－going total knee arthroplasty（TKA）. Methods：During February 2011 to March 2013，115 patients undergoing TKA were recruited in this study. These patients were assigned randomly into 2 groups：study group（n=59） and control group（n=56）. All these patients received unilateral TKA under intravenous plus inhalation anesthesia. After the surgery，patients in study group were treated with continuous femoral nerve block for the postoperative pain，meanwhile，patients in control group were treated with patients controlled intra－venous analgesia（PICA）. The level of D-dimer in plasma was detected and the ultrasonic detector was applied to estimate the DVT. Visual analogue scores（VAS） at 2，6，12，24，48，72 h after the surgery were recorded. Functional exercise was assessed with the distance of patients’ walk within 3 d after TKA. Results：After the TKA，the plasma level of D-dimer was significantly lower in study group than in control group（P=0.000 8，P=0.000，P=0.000）. The outcomes of the ultrasonic detection showed that 6 out of 56 patients in control group developed DVT after TKA，whereas 2 out of 59 patients in study group developed DVT after TKA（?字2=4.296，P=0.039）. The VAS at each time point was lower in study group than in control group. The distance was longer in study group than in control group（P=0.000，P=0.000，P=0.000）. Conclusions：Continuous femoral nerve block has better effect on DVT after TKA than PICA，which may relate with its better analgesic effect and its promotion of postoperative functional exercise.