Abstract: Identity authentication is the first safeguard for security of Wireless Sensor Networks (WSNs). Because of the efficiency and safety issues of the existing identity authentication protocol in WSNs, a low-power identity authentication protocol which is based on Shamir-threshold-secret sharing scheme is proposed. In the premise of not compromising the network’s security, the new node need to be checked by the majority of authorized nodes, therefore, the consumption of computation can be reduced effectively during the process of authentication. One-way hash function is used for encrypting communication data and also the timestamp mechanism for being against reply attacks in authentication process. Analytical results show that the protocol is low-power consumption and has the ability of resisting eavesdropping attacks, replaying attack and attack of a few nodes captured.