In recent years, enhancing the network capacity of complex networks has attracted wide attention. In reality, there are two-layer networks with logical-layer and physical-layer structures. It is meaningful to do research on two-layer networks. We proposed an improved efficient routing (IER) strategy to alleviate traffic congestion in two-layer networks. The static information and tunable parameter of the two-layer network were considered in our routing strategy. Under our routing strategy, by changing the parameter , the two-layer networks can achieve maximum traffic capacity. The simulation results showed that compared with the shortest path (SP) routing strategy and improved static weighted routing (ISWR) strategy, the proposed routing strategy can significantly improve the network traffic capacity.