According to the characteristics of human shoulder joint,a kind of flexible bionic shoulder joint is designed,and the inverse kinematics model of the bionic joint is derived.By taking the minimum output torque,the output force model and the maximum contraction ratio of the pneumatic artificial muscle as the constraint conditions and taking the maximum range of the bionic joint motion as the objective function,we use genetic algorithm(GA)to optimize the structure parameters of the bionic joint.Experiments show that the range of joint motion after optimization is obviously increased,which can effectively improve the flexibility of the bionic joint.