A roll-off parameter determining module disposed at a receiving terminal is provided. The receiving terminal receives first roll-off information of a first frame and second roll-off information of a second frame. The first frame is adjacent to the second frame. The module for determining a roll-off parameter includes: a register unit; a first determining unit, determining whether one of the first roll-off information and the second roll-off information includes a first data type, and generating a first roll-off parameter indicator; a second determining unit, determining whether one of the first roll-off information and the second roll-off information includes a second data type and outputting a second roll-off parameter indicator; and a look-up table (LUT) unit, looking up an LUT according to the first roll-off parameter indicator and a second roll-off parameter indicator to output a roll-off parameter.