In order to mitigate the performance fading of satellite-to-ground laser communication system caused by atmospheric turbulence, a multi-aperture receiving scheme based on fiber coherent beam combining (CBC) is used. A typical satellite-to-ground coherent laser communication model is considered in this paper, and the numerical simulation results of the variations in sensitivity and bit error rate of the communication system with turbulence compensation effect are given. Based on an existing beam combining method, a set of CBC optical communication receiver with four apertures is constructed, and the phase-locked bandwidth of the system under two and four apertures are measured. Then we use the rotating phase screen to simulate the influence of atmospheric turbulence on the wavefront at different Greenwood frequencies. Meanwhile, we ensure the incoherence of the received light intensity. On this basis, the relative fluctuation variances of light intensity in optical fiber before and after CBC are given. The results show that the system can effectively mitigate intensity scintillation in the weak turbulence.