Routing security is one of the most important considerations in Wireless Sensor Networks (WSNs). Currently, more and more people pay attention to this issue. But most of the secure protocols must use public key and symmetric cryptographies which induce heavy load to nodes in the whole routing stage. In this paper, we propose an Efficiency Security Model of Routing (ESMR). In routing stage, ESMR only uses public key cryptography when new nodes enter the wireless sensor network and does not use symmetric cryptography at all. Through the security analyzing, we find our cryptography method only can resist the outside attackers, but it is helpless to inside attackers. Therefore, reputation mechanism is proposed against inside attackers in ESMR. The simulation result shows that the performance of ESMR is not as good as LEACH(Low-Energy Adaptive Clustering Hierarchy routing protocol) in no attacker environment, but it becomes better and better with the number of attackers increasing.