The severe attenuation of the optical signal in laser-submarine communication increases the BER and highly influences the system performance.So the capacity of the error-correcting code must be good enough to improve the data reliability and make better communication effect.Low Density Parity Check (LDPC) code′s rates are extremely near to the Shannon limit.The composition of laser-submarine communication system is introduced firstly in this paper,and then the compiling principle of LDPC code is analyzed.By simulation,the capability of LDPC code is validated in laser-submarine communication system.The results proved that the LDPC code can decrease the system′s BER and can improve the system performance remarkably.