Abstract: Space-time coding transmission information by parallel channels of the multi-antenna array can further improving transmission rate while guarantee the quality of communication. The authors' work at orthogonal space-time block code, space-time trellis code, unitary space-time code, differential space-time code, hybrid space-time code and relevant aspects was introduced, by adopting various pulse position modulations defined negative, conjugate and complement operation, transform the coding matrix into real matrix expressed by pulse position. The relationship between system error rate and transmitting antenna/receiving antenna number, atmospheric turbulence intensity was analyzed. The error rate characteristics of differential space-time code and unitary space-time code under different atmospheric turbulence were discussed. Combination of layered space-time code and space-time block code, reasonable compromise the multiplexing gain and diversity gain, a hybrid space-time coding scheme suitable for IM/DD type optical communication was put forward.