A node expansion method for preventing scratching and collision with obstacles is provided, considering the influence of the robot"s own size and volume during its walking process. The traditional A* search method from the start point to the end point is changed to a simultaneous bidirectional search method from the start point to the end point and from the end point to the start point. The "end point" in the search process is set as the current point of the synchronous search in both forward and reverse directions, and the distance between the current point and the current end point is introduced into the evaluation function, significantly reducing the number of reciprocal searches and the number of search nodes, and improving the search efficiency. Based on the path obtained by the improved bidirectional A* search algorithm, path optimization is carried out, including the removal of redundant points on the path and the arc transition of the inflection point path successively. The simulation results show that the obstacle avoidance path obtained based on the above method has fewer search nodes, high search efficiency, smooth and stable path, and is easy for the robot to complete the obstacle avoidance path walking.