In the frequency hopping communication system, the receiver should supervise and copy the hopping frequency in the sample frequency band width timely to accomplish the digital down conversion. A method of wide band concatenated digital down conversion is proposed. The method includes two processes, channelization and the plurality down conversion. The channelization is independent and not related to the frequency offsets compensation so the whole system is less complex. The plurality down conversion is accomplished in low frequency and convenient for the frequency offsets compensation. The simulation result shows that the down conversion can be accomplished timely and the bit error rate is lower than 10-6 when the Eb/N0 equals to 12 dB.