The intensity expression of partially coherent light is obtained by using cross spectral density function in the paper.The influence of turbulence internal and external scales,coherent parameters of light source and zenith Angle on the received light intensity is analyzed.The larger the parameters of the light source,the smaller the influence of the received light intensity on the internal and external scales of turbulence in the process of atmospheric propagation at slant range.When the transmission distance is less than 4 km,the influence of turbulence internal and external scale changes on the received light intensity can be ignored.Coherent parameters have a great influence on the light intensity at a small zenith Angle.With the increase of zenith Angle,atmospheric turbulence plays a dominant role in the influence of the received light intensity,and the influence of coherent parameters of the light source on the received light intensity is weakened.Finally,the numerical simulation results are explained.