The present invention relates to method and system for managing accounting information in a mobile switching center (MSC) configured to prevent abnormal termination of calls in progress and loss of accounting information due to the abnormal termination of the calls, when system start-up request from operator terminal occurs due to software exchange, etc. Each subscriber call processing processor receives a call termination message from an operation and maintenance processor (OMP) and main process in the subscriber call processing processor transfers the call termination message to child processes in the subscriber call processing processor that currently process calls. The main process receives a response message for the call termination message indicating that calls are normally terminated and accounting information is generated from the child processes, generates final call termination completion response message and transfers the call termination completion response message to the OMP, thereby performing a normal system restart-up procedure.