Abstract: The received constellation effect of QPSK subcarrier modulation by multiplicative noise and additive noise was studied. A theoretical model of laser communication system was constructed, the received constellation of the system under multiple noise and additive noise was derived. The constellation distribution and the power spectral density of the receiver were calculated under mixed noise environment. The influence of system bit error rate in different visibilities and transmission was analyzed in detail under mixed noise environment. The results show that with the change of turbulence intensity, the receiver power spectrum has obvious broadening. When the visibility is less than the transmission distance, the atmospheric aerosol scattering is the main factor affecting the communication under different additive noise conditions; when visibility is 0.5 km to 1.5 km, the passenger noise will affect the reception light and increase the system error rate under different multiplicative noise conditions. The proposed works are very important for reducing the bit error rate of laser communication and improving the communication quality in the real environment.