The large oscillation of the weight center on the sagittal plane can produce shock and oscillating force on the shoulders and back of the human body， which can cause muscle fatigue in the upper limbs. To alleviate the impact and oscillating force， a hipjoint driven backpack exoskeleton with adaptive adjustment of the weight-gravity center is proposed. Based on the five-bar model of the human body， the kinematic model of the gravity center in the human-weight system and the human-exoskeleton-weight system is established by the D-H method to analyze the trajectory of the gravity center. Based on the Newton-Euler method， the human dy? namics model and the human-exoskeleton dynamics model are established. The changes in the human shoulder back forces and the lumbar， hip， and knee joint moments are obtained in the human-weight and human-exoskeleton-weight systems. Results are vali? dated by the software OpenSim. Kinematics， dynamics， and software simulation show that the exoskeleton reduces the fluctuation of the gravity center， improves the torque distribution of each joint， and improves the load-bearing performance.