Abstract: Presents a high speed adaptive multi-carrier underwater acoustic(UWA) communication system based on digital signal processing(DSP) real-time processing. Multi-channel freguency shift keying(MFSK) modulation, exact data synchronization and low-noise programmable gain amplifier(PGA) are used to decrease the error rate. With experiments on a condition of 1.5m depth, and 2km length, the system showed that the technique is effective in matching the real-time and voice recovery request, the transmission distance reached at least 2km, and bit-error rate(BER) below 10<sup<-3</sup<.