Abstract: Multi-hop wireless networks (MWNs) face various attacks threats, especially the internal multi-layer attacks and bad mouthing attack aiming to the routing security. As an effective method to evaluate the trust relationship between the nodes and against internal attacks, reputation mechanisms have been introduced into MWNs to preserve the routing security. Although there are a multitude of research work, most of them are based on the layered design and only considering the single layer attacks, thus ignoring the multi-layer attacks. And they also ignore the bad mouthing attack and the creditability of the recommended nodes and recommended information, which reduces the reliability of the reputation evaluation results. To solve the above problem, this paper first proposes a new reliable recommendation based cross layer dynamic reputation mechanism named CRM, and then proposes a secure routing protocol RPCSR based on the CRM. Simulation results and performance analysis demonstrate that the proposed secure routing protocol RPCSR can implement routing security preserving against the internal multi-layer attacks and bad mouthing attack effectively.