This paper introduces the models of turbulence spectrum as the laser signal propagates through the random atmospheric turbulence，analyses the scintillation effect and beam expansion effect under the condition of considering the inner-scale.It also probes into the influence of inner-scale，the wave length of laser and atmospheric structure constant on wave scintillation based on the modified Rytov method，and makes numerical simulation with MATLAB.The result indicates that the impact of inner-scale on scintillation is important，at the same time the scintillation index varies with the wave length and structure constant of atmospheric.