Objective To research the influence of gravity on lower limb motions during human walking. Methods A suspended microgravity simulation system was designed for the experiment. Biomechanics data in walking of twelve volunteers were measured by the motion capture system (Motion) and 3D force plate (Kistler) under simulated Mars gravity (1/3 G) and lunar gravity (1/6 G), and earth gravity (1 G). Results The curves of joint angle, joint force and joint torque in hip, knee and ankle joints for 12 subjects in sagittal plane within one gait cycle under different gravity were calculated and analyzed．The motion ranges of lower limb joints during human walking under different gravity were obtained. Conclusions Gravity had a major influence on lower limb motions during human walking. Under simulated Mars and lunar gravity, the motion ranges of hip and knee joints in sagittal plane were significantly decreased while the motion range of ankle joints was increased. In addition, the joint force and joint torque of lower limb joints in sagittal plane under lower gravity were also decreased a lot.