An improved congestion aware routing algorithm is proposed to solve the problem that the network is about to enter the congested state when a large number of instant concurrent data stream flow emerge in network. The algorithm can select the path according to the path length and congestion condition of the node and the neighbor node to the destination node in real time, use the ASON (Automatically Switched Optical Network) network packet congestion index as the link value, and calculate the link of each node according to the actual packet transmission status of network. It is an adaptive adjustment routing algorithm which can dynamically sense network congestion state. Simulation results show that compared with the shortest path routing algorithm, the proposed algorithm can effectively improve the transmission efficiency of transmission network and optimize the utilization rate of network resources. This work is supported by Youth Science Foundation (No. 51707135).