In order to overcome Inter-Symbol Interference(ISI) caused by multipath propagation in underwater acoustic channel
a new kind of frequency-domain adaptive equalization has been presented.It is based on the conventional frequency-domain equalization
the peculiarity of MFSK
correlation of received and reference data.It is a new structure with both equalization and demodulation.The results of computer simulation show that there is 2dB enhancement compared with conventional method.The new one are also had a good performance in practical underwater acoustic channel.