The invention discloses a layered optical spatial modulation method suitable for a turbulent flow channel. The layered optical spatial modulation method mainly comprises layered optical space modulation layer mapping and bit mapping methods, receiving end signal detection and demapping and layered optical space modulation system bit error rate upper bound calculation. The layer mapping is to divide input bit information into two layers, the bit mapping is to determine an LD serial number and a pulse amplitude or a pulse position activated by each layer according to a mapping rule, and two lasers modulated by PPM and PAM are activated at the same time to send information; and the receiving end adopts a maximum likelihood decoding detection algorithm to complete detection of the laser serialnumber and the digital modulation signal, and the transmitting end bit information can be recovered after corresponding reflection and emission. On this basis, the upper bound of the bit error rate of layered optical space modulation is derived. The construction of the layered light space modulation system effectively improves the spectrum efficiency and transmission rate of the system.