Objective To explore biomechanical characteristics of hemiplegic patients using UOHL (up obstacles with healthy leg, down obstacles with affected leg) and UOAL ( up obstacles with affected leg, down obstacles with healthy leg) to pass through obstacles, and to provide theoretical basis for reducing the incidence of falls in patients. Methods The Qualisys motion capture system and three-dimensional ( 3D) force plate were used to collect the kinematics and dynamics data of 15 hemiplegic patients passing through obstacles with normal walking mode (NWM), UOHL and UOAL, and the data were processed and analyzed. Results Compared with NWM,805 both UOHL and UOAL increased bilateral lower extremity range of motion ( ROM) to some extent. Compared with NWM and UOHL, vertical ground reaction force (GRF) of affected leg side under UOAL fluctuated more, and gait stability was worse, indicating a greater risk of falling. Conclusions When patients pass through the obstacle, the requirements for joint ROM on the side of the obstacle are relatively high, the adaptability of the affected leg side is poor. The GRF in vertical direction changes greatly during single-leg support period after touching the ground. When the body weight is completely transferred to this side, it is easy for the patient to fall. Compared with UOAL, patients can easily maintain gait stability when using UOHL to pass through obstacles, and the risk of falling will be reduced.