Objective To conduct a comparative analysis of the biomechanical characteristics of the lower limbs during stair descent in patients with hemiplegia using different methods to provide theoretical references for reducing fall risk during stair descent. Methods Ten healthy subjects and 20 patients with hemiplegia were selected, and their kinematic and dynamic data during stair descent were collected using the Qualisys Motion capture system and the Kistler three-dimensional dynamometer. Their biomechanical characteristics and fall risks were also analyzed. Results Compared with that of healthy subjects and patients that step on the healthy side (SHS), the range of motion (ROM) of the affected side in the lower-limb joints of patients that step on the affected side (SAS) was smaller. SHS reduced the flexion and extension ranges of the healthy side of the knee joint, and the ROM of the affected side in the lower-limb joints of SHS patients was greater than that of SAS patients. The ground reaction force (GRF) curve changes of SAS patients in left and right directions during stair descent were relatively consistent with those of normal subjects. The maximum vertical GRF of the affected side in SAS patients at the moment of landing was 1.05 times the body weight, whereas that of the healthy side was 1.25 times the body weight, which was lower than that of normal subjects (1.5 times the body weight). The maximum vertical GRF of the healthy side in SHS patients at the moment of landing was 1.85 times the body weight, which was higher than that of SAS patients and normal subjects. Conclusions Compared with that of SAS patients, the affected limb side of SHS patients has a greater ROM and vertical GRF at the moment of landing during stair descent, making SHS difficult to master. SAS is most consistent with the biomechanical characteristics during stair descent of patients with hemiplegia.