The long distance transmission of underwater laser pulse is simulated based on Monte Carlo method. According to the underwater broadening of laser pulse and the variation of pulse energy, the system uses a solid-state laser with the wavelength of 532 nm and the single pulse energy of 1 mJ as the emission source, and uses a telescope with the aperture of 100 mm and the field angle of 15° as the receiver. Low-density parity check codes (LDPC) and pulse-position modulation (PPM) are accomplished based on a field-programmable gate array (FPGA). The received signal after photoelectric conversion and sampling is transmitted to the host computer for post-processing. Finally, a pool experiment is used to verify the system performance based on the developed experimental system. The theoretical and experimental results demonstrate that the designed system with LDPC and PPM can obtain 2.34 dB coding gain at the same bit error rate (BER) under the condition of Jerlov Ⅱ water quality. Experiment shows that the system can achieve reliable underwater communication with BER of 10-5 and distance of 130 m.