A method of preventing call drop in a mobile terminal when a serving radio network subsystem SRNS relocation to a target RNC from a source RNC is performed includes (a) receiving a control message in accordance with start of the SRNS relocation from the target RNC, (b) performing a RLC configuration procedure, (c) transmitting a complete message in accordance with the RLC configuration procedure to the target RNC, and (d) retransmitting the complete message to the target RNC in case that RLC reset is performed after the complete message is transmitted. As a result, call drop by exceptional case while the SRNS relocation is performed may be prevented.