Abstract: According to the security problem existing in current key management scheme of wireless sensor network, an authenticated key establishing scheme (EMSR) which is used in wireless sensor network and can be proved to be safe is put forward. By applying public key certificate, the mutual authentication is realized. At the same time, the authentication problem caused by the absolute use of symmetric encryption mechanism can be efficiently avoided. In CK security model, security proof for EMSR protocol has been carried out and the performance of key establishing scheme based on several kinds of public key mechanism has been analyzed. The results of security proof and performance analysis show that the EMSR has the advantages on the responding security properties in security model and supporting the net node whose resources are limited, and satisfies the communication requirements of wireless sense net.