In digital radio communication, diversity reception can combat flat fading and adaptive equalization can combat Inter-Symbol Interference (ISI). In this paper, the structure and algorithm of a multi-channel equalizer with combined diversity reception and adaptive equalization techniques are studied. Because Phase-Looked-Loops (PLL) are embedded in the equalizer, this equalizer is suitable for coherent communication in channels with high phase fluctuation. Monte Carlo simulation is used to test its performance and the results show that a multi-channel decision-feedback-equalizer has better performance than a single-channel decision-feedback-equalizer, and the results of processing high-speed digital underwater communication signals demonstrate this farther. In digital paper communication, diversity reception can combat flat fading and adaptive equalization can combat inter-Symbol Interference (ISI). In this paper, the structure and algorithm of a multi-channel equalizer with combined diversity reception and adaptive equalization techniques are are.. Phase-Looked-Loops (PLL) are embedded in the equalizer, this equalizer is suitable for coherent communication in channels with high phase fluctuation. Monte Carlo simulation is used to test its performance and the results show that a multi-channel decision-feedback- equalizer has better performance than a single-channel decision-feedback-equalizer, and the results of processing high-speed digital underwater communication signals demonstrate this farther.