Aiming at known global static environment, this paper conducts research on path planning strategy for mobile robot from the aspect of single robot. One stepwise path planning method is proposed as follows. Model of robot operation space is established through link graph at first, then the shortest path of link graph is obtained by graph theory algorithm. Particle Swarm Optimization algorithm is employed to optimize the obtained path so as to achieve global optimal path at last. Simulation results show that the proposed method can accomplish the planning of robot moving path from the from the start state to target state at short length without any collision. The proposed method is simple and feasible, able to satisfy high real-time requirement of mobile robot navigation, which provides a satisfactory solution for robot path planning.