Objective To study the intrinsic relationship between hemiplegic gait features and abnormal muscle strength of lower limbs, so as to elucidate the muscle strength causes of hemiplegic gait and provide recommendations for its clinical treatment. Methods Models of hemiplegic gait and normal gait were established for simulation, and the validity of the models was verified by comparing the simulation model with measured data of the normal gait. The differences in kinetic data, ground reaction force (GRF) and muscle force between the two models were analyzed to explore the different dynamic characteristic of hemiplegic gait and normal gait. Results The complex correlation coefficient between LifeMOD simulation results and measured data was 0.922, indicating that the established dynamic model was reasonable and effective. Hemiplegic patient with low tibialis anterior muscle strength led to ankle dorsiflexion inadequacy during initial ground period, and low gastrocnemius muscle could not achieve the promoting effect from ground during preswing period. Conclusions The strength weakness of tibialis anterior muscle and gastrocnemius are the main reasons for foot drooping and other hemiplegic gait characteristics. LifeMOD modeling and simulation can assist the diagnosis of abnormal muscle strength in hemiplegia patients.