A method and apparatus for determining frame quality in a mobile communication system determines frame quality by estimating a received SIR without using a CRC under a control hold state in which PCBs are only transmitted while no data transmission actually occurs. The method for determining frame quality includes estimating a signal to interference ratio of an allocated traffic channel from PCBs extracted from PCGs of a frame received through the traffic channel and a signal received through a pilot channel received during a section of the PCGs in a state that no data transmission occurs between a mobile station and its control system and the PCBs are only transmitted and received through the traffic channel; and comparing the estimated signal to interference ratio with a preset reference signal to noise power ratio to determine quality of the received frame.