This paper analyzes the influence of haze on the performance of ground space optical communication (GSOC). Firstly, the scattering model of haze aerosol is established based on the coated scattering theory of Christian Mätzler. Then the fitting relationship between atmospheric visibility V and PM 2.5 is obtained according to the Meteorological Bureau of Beijing. In order to calculate the attenuation coefficient, the relationship between spectral distribution of aerosol particles and PM 2.5 Index is derived. Finally, the effect of haze on GSOC with different detectors and modulation modes are discussed. The result shows that with the increase of PM 2.5 Index, the received optical power, sign-to-noise (SNR) and channel capacity (CAP) decrease rapidly, and bit error rate (BER) increases rapidly. In terms of wavelength selection, under the same detector and modulation mode, the effect of haze on the GSOC of the 0.86um laser is greater than that of the 1.55um laser. In the modulation method, the use of Binary Phase Shift Keying (BPSK) modulation is better than the use of Quadrature Phase Shift Keying (QPSK) in order to reduce the BER, while the worst modulation is to use On-Off Keying (OOK). When the sensitivity of the detector is -35 dBm，the value of PM 2.5 corresponding to 1.55um is not higher than 557, and the value of PM 2.5 corresponding to 0.86um is not higher than 548.