Vertical bell labs layered space-time (V-BLAST) is a technology combining space multiplexing with space diversity. It has the high spectrum efficiency and the transmission speed, so the technology is applied to free space optical communication. In this paper, after researching the characteristic of atmosphere channel, a free space optical communication channel model based on V-BLAST is proposed. Code principle of V-BLAST is introduced, and channel capacity of this system is analyzed. The difference of the channel capacity and error rate of the system with and without V-BLAST structure is compared through simulation experiment. As a result, when receiving antenna number is larger than the transmitting antenna number, the channel capacity is improved directly proportional with transmitting antenna number, and the error code performance of system coded V-BLAST is improved effectively. It shows that the system has channel capacity supplied by V-BLAST structure and well error code characteristic, and the scintillation effect caused by atmosphere turbulence is effectively overcome.