At present, SDN controllers such as NOX and FloodLight provide the shortest path forwarding algorithm similar to the traditional router OSPF protocol. These algorithms collect the global parameters of the switch through the SDN controller, but do not take advantage of the SDN system to obtain runtime dynamic information to optimize the performance of the algorithm,traditional algorithms are prone to network congestion when traffic is too large.This paper mainly studies the routing algorithm of SDN, proposed the application of particle swarm optimization algorithm, combined with the characteristics of SDN technology to optimize the network load.The simulation results show that the proposed algorithm can improve the overall utilization of the network and reduce the congestion of the network to a certain extent.