The existence of atmospheric turbulence and platform micro-vibration will cause the random channel attenuation of the satellite-to-ground laser communication links， which leads to the unstable communication quality. To further analyzes the performance of satellite-to-ground laser communications with the influence of atmospheric turbulence and platform micro-vibration， a random attenuation model of joint satellite-to-ground laser link is established. Based on binary phase shift keying modulation and heterodyne coherent reception， the closed form expression of system average bit error rate under the model is given. The influence of different satellite-to-ground laser communication system parameters on the bit error rate performance is analyzed by simulation. The research results can provide a theoretical reference for the design of practical satellite-to-ground laser communication system.