The present invention provides an NAS (Network Access Server) information recovery method and a network authentication server. The network authentication server analyzes the operation request of a user terminal to judge whether the NAS information of the user terminal is lost; when the network authentication server judges that the NAS information of the user terminal is lost, the user terminal sends a request for obtaining the NAS information to an NAS to obtain the NAS information and sends the acquired NAS information to the network authentication server, so that the network authentication server can generate an NAS information key corresponding to the NAS information of the user terminal after saving the NAS information and sends the NAS information key to the user terminal for saving the NAS information key; and therefore, when the NAS information is lost, the user terminal can directly access the NAS so as to obtain the NAS information, the NAS information key in the user terminal can be recovered, and a user is unaware of a whole process, and therefore, user experience can be improved.