Abstract:The performance of free-space laser communication system is easy to be affected by the atmospheric turbulence. Considering the practical situation of air-to-ground laser communication,the modified Rytov method is applied in the optical wave propagation in the slant path under atmospheric turbulence. Based on the ITU-R turbulence structure constant model,a mathematical calculation model of bit error rate under atmospheric turbulence conditions is established;Through the bit error rate calculation under turbulence channel of different intensities,effects of system parameters,like communication height,zenith angle,wavelength,the near surface wind speed etc. on the bit error rate are discussed. The results show that the intensity of atmospheric turbulence is the decisive factor affecting the system performance.Under the same intensity of turbulent,the system′s bit error rate increases with the increase of communication height,zenith angle,wind speed near surface,and decreases with the increase of the wavelength.