To settle the problem of insufficient stability and easy to fall into local extreme values in mobile robot path planning by using ant colony algorithm,an improved multi-step ant colony algorithm was proposed.The movement mode in the basic ant colony algorithm which could only move in one step with a fixed direction was improved,so the turning times and the path distance were reduced.For the situation that the robot might encounter a large slope in actual work,the height factor was added into the heuristic function to improve the adaptive capacity of the algorithm to the environment.Adaptive volatilization mechanism was adopted to accelerate the convergence speed and efficiency of the algorithm.The results show that compared with the basic ant colony algorithm,in the environment with variable hight,the path planned by using the improved multi-step ant colony algorithm is more gentler and shorter,so the designed method is more suitable for the actual operating environment of robot.