Abstract: Multi-channel decision feedback equalizer (MC-DFE) is the main method to overcome multipath fading and eliminate inter-symbol interference (ISI) for underwater acoustic coherent communication. A diversity combination self-optimized adaptive multi-channel decision feedback equalizer is proposed. It consists of fast self-optimized LMS diversity combination (FOLMSDC) algorithm,fast self-optimized LMS (FOLMS) algorithm and fast self-optimized LMS phase compensation (FOLMSPC) algorithm. The proposed algorithm not only can reduce computation complexity,but also improve receiver performance because its step-size factors and phase tracking factors can be adaptively updated with the varying underwater acoustic channel. Simulation experiment results show that the proposed algorithm performance is better than current available algorithm.