Objective To investigate the influence of gravity levels on lower limb motions during human walking. Methods A suspended microgravity simulation system was designed for the experiment. Kinetic parameters from lower limb joints of twelve volunteers during walking were measured by the motion capture system and 3D force plate under simulated Mars gravity (1/3 G), lunar gravity (1/6 G) and earth gravity (1 G). Results Under simulated Mars and lunar gravity, the ranges of motion (ROMs) of hip and knee joints in sagittal plane significantly decreased (P＜0.01) while the ROMs of ankle joints obviously increased (P＜0.05). The ROMs of hip, knee and ankle joints in sagittal plane under earth gravity were 45.2°, 67.7°, 32.5°, respectively, while the ROMs of hip, knee and ankle joints under lunar gravity were 25.1°, 50.8°, 42.4°, respectively. In addition, the force and torque of lower limb joints in sagittal plane under lower gravity also decreased significantly (P＜0.01). Conclusions The results obtained by this study were almost the same as the research findings obtained by using treadmill. Astronauts can use the treadmill and microgravity simulation system for walking exercises under lunar gravity on the earth.