In order to analyze the influence of atmospheric turbulence on laser signal transmission，based on the theory of random signals and stochastic processes，the signal-to-noise ratio (SNR) and bit error rate (BER) formula is derived for wireless laser communication system，the effect of the scintillation index，atmospheric structure constant and laser wavelength on the SNR and the bit error rate is explored，and under different atmospheric structure constant and different laser wavelength，the signal-to-noise ratio and bit error rate with the change of transmission distance are studied by numerical simulation. The results show that：under the weak fluctuation condition，the scintillation index increase will reduce the communication quality of the system; the atmospheric turbulence has a significant impact on signal-to-noise ratio and bit error rate of laser communication system. Comparison with the effect of different laser wavelengths on the system，the long wavelength laser signal can increase effective distance of the signal transmission，restrain the growth of BER and improve communication quality of wireless laser communication system.