Light intensity fluctuation in the cross-section caused by atmospheric turbulence increases the bit error rate(BER) of laser communication system. The effect is analyzed using the theory of light propagation in the atmosphere based on the Rytov approximation under the suitable assumptions of isotropic Kolmogolov spectrum of turbulence, and the BER of laser communication system and atmospheric turbulence are combined in terms of signal detection theory. The analysis results turn out that, measured by BER, the effective distance of laser communication system shortens greatly along with the increasing of [EQUATION] under the environment of typical marine atmospheric turbulence, the effective distance is less than 2 km when [EQUATION] is equal to 5[EQUATION] m[EQUATION], and the distance even shortens to 1 km when [EQUATION] reaches 3[EQUATION] m[EQUATION].