Abstract: In this paper, we puposed a Two Directions ant colony algorithm and apply it to robot path planning in static environment.We changed grid method into expdnded grid method for the environmental models.The optimal path search is finished by two trible's ants opposite crowing from starting point and ending point.Heuristic information is calculated by the coordinate of Starting point, ending point and the posion of ant.Pheromone is reserved by direction pheromone matrix.Resultsof simulation experiments demonstrate that even in obstacles very complicated geographical environment the best path can be found in short time.