The present invention relates to a method and system for management of the mobility of a terminal by using a non-access stratum (network stratum “NAS”) protocol in a mobile telecommunication network. The method for management of the mobility of a terminal by using an NAS protocol, i.e., messages includes a terminal (“UE”) and a mobile management entity (“MME”), and efficiently divides and processes security protected NAS messages and NAS messages with no security, and efficiently divides and processes EMM (EPS Mobility Management) messages, i.e., mobility management messages, and ESM (Evolved Session Management) messages, i.e., session management messages in a network such as an EPS (Evolved Packet System) of 3GPP, thereby managing the mobility and the sessions of a terminal in an efficient manner.