It is difficult to resolve the phase compensation problem in the coherent optical communications using theoretical analytical method. To solve the problem, the split-step beam propagation method is used to study the influence of the atmospheric turbulence on satellite-to-ground coherent optical communication. The simulation model of the laser propagation in the turbulence is established. And then the geostationary earth orbit(GEO) satellite-to-ground downlink laser propagation is simulated. The simulation results are in a good agreement with the theoretical results, which proves the validity of this method. At last, using this simulation method, the fading coefficient and bit error rate of binary phase shift keying (BPSK) coherent optical communication are calculated and analyzed.