System and method for processing message in mobile communication system

A system and a method for processing messages in a mobile communication system are provided to reduce overhead, resulted from the operation for determining whether encryption is used for each packet received through each channel. A mobile terminal(400) generates a message at a user's request, encrypts the message, and transmits the encrypted packet through a radio channel. If it is indicated that the packet received from the mobile terminal(400) was encrypted, a base station(410) requests encryption information of the mobile terminal(400), which has transmitted the packet, from a PCF(Packet Control Function)(420) and receives the encryption-related information of the mobile terminal(400) from the PCF(420) before decrypting the encrypted packet. The PCF(420) receives the request for the encryption information of the mobile terminal(400) from the base station(410), and transmits the encryption-related information of the mobile terminal(400) to the base station(410).