A look-ahead equalizer is provided. The equalizer has an equalizer without a first tap, a look-ahead unit, and a slicer unit. The equalizer without a first tap outputs a pre-filter output and a state reference signal. The look-ahead unit is coupled to the output of the equalizer without a first tap for generating a first, a second, and a third equalizer look-ahead values according to the state reference signal. The slicer unit is coupled to the look-ahead unit. The slicer unit comprises plural state slicer units. Each state slicer unit receives the first, the second, and the third equalizer look-ahead values, and then selects one of them according to a comparison result of the state slicer unit and the state reference signal.