A novel path planning approach based on particle swarm optimization (PSO) and ant colony optimization (ACO) algorithm is presented aiming at mobile robots in complex environment. Firstly the algorithm makes use of the method of environment modeling of particle swarm to quickly plan a initial path from the starting point to the goal point of the path. Then pheromone is distributed based on the paths generated before. At last, an improved ant colony optimization is used to find the eventually best path. The simulation shows that this method can greatly reduce the searching time, especially in complex environment.