A security protection method and an apparatus to implement security protection for a plurality of non-access stratum (NAS) connection links. The method includes determining, by a terminal, a first parameter, where the first parameter is used to indicate an access technology used to transmit a non-access stratum NAS message. The terminal can support at least two access technologies, and can separately maintain a corresponding NAS COUNT for each of the at least two access technologies. The method further includes performing, by the terminal, security protection on the NAS message based on the first parameter, a NAS key, and a NAS COUNT corresponding to an access technology used to transmit the NAS message.