The coordinates of the marked points of joints and the changes of foot force in the human walk motion are obtained with systems of motion image acquisition and force measuring. The effects of kinematics and dynamics on the human lower limb in different loads (0, 10, 20, 30 kg) and walking speeds (0.8, 1.3, 1.7 m/s) have been investigated using the human dynamics model,. The results were as follows. First, with the increasing load, the dorsiflexion angle of ankle joint increased during the procedure of toe-off, the range of motion of the knee joint decreased, the flexion angle of the hip joint increased, and oppositely, the extension angle of the hip joint decreased. Second, with the increasing speed, the range of motion of the ankle joint, the maximum flexion angle of the knee joint, the flexion angle, extension angle of the hip joint and the range of motion of hip joint increased. Finally, the torque and power of the ankle joint, the knee joint and the hip joint increased with the increasing speed and load. The results can provide an important basis for the mechanism design of lower limb power-assisted exoskeleton.walking gait, dynamical model, motion analysis, load walking Citation:Han Y L, Wang X S. The biomechanical study of lower limb during human walking. Sci China Tech Sci, 2011, 54: 983−991,The motion of human walk is very complex. It is a result of synergic movement of skeleton around the joint and powered by several rhythmic muscles contraction. With the development of modern measuring technique, it is possible for us to analyze the diversification of the walking lower limb in kinematics and dynamics more precisely. Now this research work is towards a special branch of biomechanics called gait analysis [1]. The researches started early overseas and mainly focused on analyzing the characteristics of the movements. Most of the results were used in athletic training, evaluation of rehabilitation exercise and the design of walk assisting device [2][3][4][5][6]. The same researches in China started relatively late, and is now mainly on the gait analysis in walking motion of the normal lower limb or the patients without any weight bearing, which are mostly used in rehabilitation evaluation [7][8][9][10]. This paper focuses on the gait analysis of normal lower limb with different loads and walking speeds, and aims at instructing the design of the power-assisted walking exoskeleton. The exoskeleton should be placed in parallel with the lower limb and match the degrees of freedom of joints. But if all the joints are powered, not only a lot of energy will be consumed but also the complexity of the control system will increase. As shown in the existing researches [11], in different stages of walk, the joint power may be positive or negative. The purpose on saving energy can be achieved by releasing the energy of positive power which is stored in a negative stage. So the work conditions of the joints should be studied while the joint torque and the joint power in the walking can also be obtained by biomechanical st...