In order to study the average bit error rate performance of satellite-ground laser communication system under the combined influence of atmospheric turbulence, pointing error and various noises. In this paper, a combined attenuation model of atmospheric turbulence and pointing error is established using the Gamma-Gamma channel model, and a closed expression for the average bit error rate of the satellite-ground laser communication system with respect to the combined attenuation model is derived by combining various noises. The research results show that when the satellite orbit altitude is 400 km, zenith angle is 45 °, wavelength is 1550 nm and the normalized ratio of equivalent beam and the pointing error displacement standard deviation（jitter） is 4, the average bit error rates corresponding to total noise, thermal noise and background noise are 1.519×10-7、6.907×10-8、1.357×10-8 respectively.