The routing protocol design for ad hoc networks is studied in this paper. First, we propose an end-to-end congestion relief routing protocol (ECRR) for ad hoc networks. Through sensing the hop count and congestion information of available paths, ECRR can select an appropriate route for data transmission. Based on ECRR and combining the advantages of single-path and multi-path routing strategies, we further develop a mixed-path end-to-end congestion relief routing protocol (M-ECRR). According to the current network state information, M-ECRR decides whether or not to execute the multi-path scheme. When the path length is small and network load is light, M-ECRR operates the single path strategy; otherwise it operates the multi-path strategy. Finally, we conduct extensive OPNET simulations to validate the performance of proposed routing protocols. The results indicate that compared with AODV, ECRR and M-ECRR can improve the network throughput, reduce the hop count and energy consumption, while ensuring the delay performance and control overhead.