In atmospheric laser communications, light intensity flashing caused by turbulence severely interferes the performance of communication system and increases the bit error rate (BER) of the system. Multi-aperture reception is the effective method to overcome the above interference. The reception areas of multi apertures and the effect of aperture position relation on space smoothing factor are analyzed. The reception performance of three apertures, is mainly analyzed and smoothing factor of multi-aperture reception is compared with that of single-aperture reception. The probability density function of light intensity fluctuation deriving from the Gamma-Gamma channel modeling from weak turbulence band to strong turbulence band is deployed to analyze the BER of multi-aperture reception system. The result shows that multi-aperture reception system can better improve the light intensity fluctuation of reception area and decrease system′s BER. With the increase of the number of aperture, the aperture smoothing factor and BER will be decreased.