Optical wireless communications using sub-carrier phase shift keying (PSK) intensity modulation through atmospheric turbulence channel is investigated. Sub-carrier PSK intensity modulation is compared against on/off key (OOK) modulation in the atmospheric turbulence channel. The simulation results show that sub-carrier PSK intensity modulation is superior to OOK in the presence of atmospheric turbulence. On this basis,the low density parity check (LDPC) codes and BP iterative decoding algorithm are applied into the optical wireless communication system,and it is simulated in the atmospheric turbulence channel with combination of 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 above scheme can satisfy the need of optical wireless communication system.