The invention discloses a wireless sensor network switching and pre-authenticating method based on evaluation, comprising the steps of: 1, predicting a new subnet to be switched by a mobile node, evaluating and predicting the mobile node, and making a pre-authenticating request; 2, evaluating the mobile node by the original subnet cluster head node, if the evaluation is safe, sending pre-authenticating information to a new subnet cluster head node; 3, evaluating the new subnet by the new subnet cluster head node, and authenticating the identity of the mobile node, if the evaluation is qualified, passing the authentication, agreeing to access, and sending evaluation information to the original subnet cluster head node; 4, deciding whether agreeing to access or not by the original subnet cluster head node according to the request of the mobile node and the evaluation on the new subnet, giving an adjustment suggest; and 5, if agreeing to access, negotiating a private key between the mobile node and the new subnet cluster head node. The invention has the advantages of short time delay, high safety and long service life of a sensor network, and can be applied to the field of sensor networks with high requirements for time delay and safety.