Topspin is one of the most attacking strokes in table tennis, and topspin forehand loop is an effective way to score. The aim of this study was to investigate the kinematics of the lower extremities in topspin forehand loop between different levels via OpenSim Musculoskeletal Modelling. Ten elite athletes (NL1) and ten medium athletes (NL2) performed the topspin forehand loop without muscle and joint injuries. An eight-camera Vicon motion capture system was used to measure the kinematics data. During the topspin forehand loop, the forward phase (FP) and the entire phase (EP) of the NL1 were significantly shorter than that of the NL2. In the sagittal plane, NL1 significantly had greater hip and ankle flexion and extension at range of motion (ROM) but less hip flexion and knee flexion at FP and less ankle flexion at BP than NL2. In the frontal plane, NL1 displayed less ROM in the hip joint and significantly less hip abduction ROM at the backward phase (BP). In the transverse plane, NL1 had a significantly greater ROM in the hip joint and displayed significantly less hip ROM at the BP. The level differences presented in this study could help table tennis athletes to improve performance and coaches to develop technical training.