Aiming at the problems of long time-consuming and large memory consumption of A* algorithm in solving path trajectory, this paper proposes an improved A* algorithm based on adaptive step. Firstly, the priority order of the search direction is set according to the position relationship between the current point and the end point, reducing the redundant planning calculation on unreasonable directions. Secondly, the judgment condition for reaching the end point is modified to achieve path jumping during trajectory planning. Thirdly, an adaptive step size strategy is proposed to improve the efficiency of A* algorithm in trajectory planning. Finally, an eight-directional search method is proposed to address the issues of large memory usage and possible memory overflow when facing large maps. Experimental results show that compared with the original A* algorithm, the improved A* algorithm greatly improves the efficiency of trajectory planning, and the problem of large memory usage is also well solved.