The causes of fog,the relevant mathematical models and its influence on atmospheric laser communication system are analyzed.In order to overcome the influence of fog on wireless optical communication link,the LDPC codes as channel coding are applied into atmospheric laser communication system,and it is simulated in the foggy atmospheric channel with combination of BP iterative decoding algorithm and sub-carrier PSK intensity modulation.The simulation results show that LDPC codes have excellent error correction capabilities and access to a larger coding gain,and the proposed scheme can satisfy the need of atmospheric laser communication system.