A digital broadcast system and method of processing data are disclosed. A channel equalizer includes a frequency domain converter receiving a known data sequence, when the known data sequence is periodically inserted and transmitted in general data, and converting the received data to frequency domain data, a CIR estimator using the data being received during a known data section and known data generated by a receiving system, so as to estimate a CIR, a CIR calculator interpolating or extrapolating the CIR estimated by the CIR estimator in accordance with characteristics of the general data being received, a coefficient calculator converting the CIR being outputted from the CIR calculator to a frequency domain CIR and calculating and outputting an equalization coefficient, and a distortion compensator multiplying the equalization coefficient calculated by the coefficient calculator with the data converted to frequency domain data by the frequency domain converter, thereby compensating channel distortion.