Multi-degree of freedom series robots are used in various fine work scenarios. The redundant Degree of Freedom (DOF) robots have excess degrees of freedom and can easily avoid obstacles, their own singularities and joint limits. But the dynamics model of redundant DOF robot is complicated, difficult to solve and slow to calculate. These are not conducive to the monitoring and analysis of the robot's state. A method of robot dynamics calculation based on wavelet approximation is proposed in this paper. Firstly, the robot dynamics model is established based on Lagrange method. Then, a multi-dimensional analysis model of robot dynamics wavelet approximation is established.