This application provides a network authentication method, a network device, a terminal device, and a storage medium. In one aspect, in this application, a network device generates a symmetric key by itself, and generates a correct sequence number of a terminal device in real time by using a first sequence number. In other words, in this application, the network device does not need to store the symmetric key and the correct sequence number of the terminal device, but generates the symmetric key and the correct sequence number of the terminal device in real time. Therefore, storage load of an HSS in the prior art can be reduced.