Aiming at the problem that Dijkstra algorithm can not plan conflict free path in multi AGV system, an improved Dijkstra algorithm based on time window is proposed after analyzing the implementation principle and limitations of Dijkstra algorithm. In the process of Dijkstra algorithm traversing from the starting node to other nodes step by step, the time window conflict judgment of each path node is introduced. By changing the backtracking vector, a shortest path without conflict with other AGV paths is obtained. Finally, the MATLAB software is used to design the corresponding program to verify the algorithm. The simulation results show that the improved Dijkstra algorithm with time windows can effectively plan the shortest path without conflict among the AGVs when planning the multi AGV task path.