An improved A* algorithm was proposed to address the problem of planning a safe and obstacle-free path for construction robots on construction sites. Firstly, by optimizing the search point selection strategy of the A* algorithm, on the basis of the 8-neighborhood node search used in the traditional algorithms, it was extended to 24-neighborhoods for search and partially discarded. At the same time, obstacles were inflated to leave enough safe distance to avoid collisions during motion. Then, the heuristic function in the evaluation function was improved by introducing the obstacle ratio K. Finally, for the inflection points in the path, Bezier curves were used to smooth the path and improve its continuity. The experimental simulation results show that the search node count, path length, and planning efficiency of improved A* algorithm are higher than those of traditional A* algorithm, and the path is smoother. The proposed algorithm effectively improves the search efficiency of paths and enhances the feasibility of global routes for construction robots, providing reference for path planning of construction robots.