Serious multi-path interferences and frequency selective fading of underwater acoustic channel will increase average bit error rate of FH-FSK system. In addition

received signals tend to be subjected to timeselective fading due to movement of AUV platform

and it will occur a series of burst errors or even lead to communication interruption. The above two factors will reduce reliability of mobile FH-FSK system

aiming at this problem

polynary low density parity check（ LDPC） code combined with FH-FSK system

present an underwater acoustic polynary LDPC code-based FH-FSK system is proposed. Experimental results show that compared with the convolution code based FH-FSK system

the binary-LDPC code-based FH-FSK system has stronger antiinterference ability. Simulation and experimental results show that the polynary LDPC code-based FH-FSK system has stronger auti-interference ability

and reliability of FH-FSK system can be further improved.