Gamma-Gamma model is a commonly used intensity scintillation model in wireless optical communications. For the problems of the complexity of the parameters models and the lack of reference for various approximate models, under Gaussian beam and using the method of simulation calculation, we analyze the effects of waveform condition, aperture dismeter, transmission distance, inner/outer scale, turbulent strength and wavelength on the characteristics of Gamma-Gamma model. The simulation results show that the effects of waveform condition, aperture diameter, transmission distance and turbulent strength cannot be ignored, while the effects of inner and outer scales, wavelength can be neglected. Moreover, as long as the ratio of aperture diameter to transmission distance remains unchanged, the Gamma-Gamma distribution characteristics will also keep unchanged. These conclusions provide reference and basis for the simplification of models in practical applications and the setting of system parameters for actual system.