An apparatus for detecting synchronization of a Broadcasting Channel (BCH) in an asynchronous mobile communication system. A Viterbi decoder calculates a zero state path metric and a minimum path metric through an Add-Compare-Select (ACS) process and a trace-back process while decoding a frame of a received BCH. A Cyclic Redundancy Check (CRC) checker performs CRC check on the decoded BCH frame. A controller detects Transmission Time Interval (TTI) synchronization of the received BCH using the CRC check result and a result obtained by comparing a difference between the zero state path metric and the minimum path metric with a threshold.