Abstract: Objective To investigate the clinical effect of external insertion of intramedullary nail in semi knee extensor for the treatment of tibial shaft fractures. Methods Forty-six cases of tibial shaft fracture patients were selected as studying object from the Second Department of Orthopedics of Jinhua Guangfu Hospital in Zhejiang from June,2012 to October,2014.All the patients were randomly divided into observation group(n=23) and control group(n=23) according to the random number table.The observation group were treated with external insertion of intramedullary nail in semi knee extensor,and the control group underwent conventional incision in patellar tendon or lateral patellar tendon approach.With 6 to 12 months' follow-up,range of motion of the knee and ankle joint,healing time and complications of two groups were compared. Results The excellent rate of observation group(91.30%) were higher than control group 56.52%(P<0.05),while the total complication rate(4.35%) was lower than the control group(39.13%),which is statistically significant(P<0.05).The postoperative knee flexion(142.36±7.82)°,extension angle of dorsiflexion(9.85±0.82)°,plantar flexion degree(22.85±5.42)° and plantar flexion (48.32±3.45)° of observation group was higher than those of the control group(132.14±4.58)°,(1.25±0.22)°,(15.62±6.33)°,(32.59±4.78)°,P<0.05.The load time (2.45±0.62) months,the callus appears time (2.52±0.48) months,the healing time (8.42±2.22) months,and the removal of fixed time (10.22±3.56) months of observation group were shorter than those of the control group (3.78±0.56) months,(3.89±0.72) months,(10.48±2.69) months,(12.89±3.79) months(P<0.05),and postoperative pain score(4.02±1.12) points was lower than the control group (7.26±2.12) points(P<0.05). Conclusion External insertion of intramedullary nail in semi knee extensor for the treatment of tibial shaft fractures can effectively improve the clinical treatment of patients and reduce postoperative complications,beneficial for the patients to improve their joints function in addition to promoting their rehabilitation..