The scintillation index of plane wave propagating through weak turbulent atmosphere, which contains Kolmogorov turbulence and non-Kolmogorov turbulence, are studied by using the numerical methods. The impacts of propagation distance on the irradiance scintillation index are analysed, and the impacts of spectral power law values and the percentage of non-Kolmogorov are also considered. The scintillation effects of plane wave propagation in mix turbulent path and in single turbulent path with Kolmogorov turbulence or non-Kolmogorov turbulence are compared. The results show that the scintillation index increases with the percentage of non-Kolmogorov turbulence increasing for one spectral power law, while Kolmogorov turbulence does the opposite in conditions of mix turbulent path. Besides, as the power law increases, the non-Kolmogorov scintillation index increases with power law up to the peak value, and then decreases with the further increase in power law in weak turbulent atmosphere.