The current paper proposes a novel algorithm to construct an efficient path for each joint of the weightlifting robot based on the proposed "momentum method". The Dijkstra Algorithm, a typical searching method in Artificial Intelligence, is adopted to obtain the shortest path. A novel idea is proposed to improve the efficiency of Dijkstra Algorithm so that it took less time to search for solutions with high accuracy. In order to obtain a high efficiency computing processes in dynamics, we formulize the optimal path with the discrete grid points based on the B-spline theory, so that we can calculate the angular velocity, angular acceleration and moment more precisely. The path planning dynamic model of three joints weightlifting robot is presented. The results of simulations demonstrated the effective and practical work with the proposed method in this paper.