An equalizer is controlled using a sync signal in a digital vestigial sideband system is provided, in which the sync signal is accurately separated even though a ghost having a short delay time and a large size is generated. A switching unit is provided between a matched filter and the equalizer, which selects one of two input signals according to rejection filter on/off control signals and separates a data segment sync signal and a data field sync signal from the selected input signal. A control signal is produced via the separated sync signal to control the equalizer to operate in one of a blind mode and a training sequence mode. Since the equalizer performs sync signal separation by using the ghost removed signal, a system initial operational time becomes shorter, and accurate sync signal separation is possible even if severe ghosts occur, to thereby improve degeneration of system performance greatly.