Path planning is one of the focuses of soccer robot research. The previous path planning algorithms ignore the influence of the players' movement on their surrounding areas, leading to the insecurity of the actual optimal safe path. In order to solve this problem, an A^* algorithm for dynamic obstacle avoidance is proposed. The method divides the football pitch according to the influence of the dribbler and the opposing defensive players, and sets the risk value for each area, and then uses the improved A^* algorithm to plan the path. The experimental results show that this method can effectively reduce the possibility for the player with the ball to be surrounded by the other defensive players, and the length and the security of the optimal security path are considered synthetically. The planned path's performance is proved to be better.