Abstract: [Objective] To measure the gait parameters of the affected limb before and after total knee arthroplasty (TKA) using a portable dynamic gait analysis system, evaluate the characteristics of gait changes, thereby guiding postoperative rehabilitation and obtaining an applicable assessment method in clinical practice. [Methods] Gait analysis was conducted with the portable dynamic gait analysis system before and 3 months after the TKA, respectively, to evaluate the improvement degree of each gait parameter before and after the operation. [Results] Compared with those before operation, the patients got significant improvements 3 months postoperatively in terms of the stride length [(81.9±2.6) cm, (110.6±7.4) cm, P＜0.001], stride height [(10.5±2.2) cm, (20.6±1.5) cm, P＜0.001], unilateral total support time [(49.1±3.1)%, (63.8±1.1)%, P＜0.001], unilateral swing time [(50.9±3.1)%, (36.2±1.3)%, P＜0.001], single foot support time [(30.1±0.5)%, (35.3±0.7)%, P＜ 0.001], landing elevation [(11.7±1.6)°, (19.5±1.4)°, P＜0.001], liftoff elevation [(47.4±1.6)°, (60.7±2.8)°, P＜0.001] and maximum swing speed [(2.7±0.2) m/s, (3.9±0.3) m/s, P＜0.001] of the affected lower extremity. However, the patients remained inferior to the normal persons 3 months after TKA in terms of landing elevation [(19.5±1.4)° vs (20.5±1.5)°, P=0.012] and maximum swing speed [(3.9±0.3) m/s vs (4.1± 0.2) m/s, P=0.006]. [Conclusion] The patients have significant gait improvements 3 months after TKA. The portable dynamic gait analysis system can quantitatively evaluate the gait characteristics of patients before and after TKA, and might have targeted guiding value for rehabilitation exercises.