Time delay of atmospheric aerosol particles and its effect on the path difference of laser were discussed. Using two-frequency mutual coherence function,the equation of path difference in the discrete random medium was obtained and the relation between the path difference with the number density and diameter of particle was established. A new method for calculating the path difference caused by time delay of aerosol particles was presented,and the path difference was calculated by using typical modes provided by optical properties of aerosols and clouds (OPAC) package in satellite laser ranging. Results show that,when the wavelength of laser is 1064 nm and the mode radius of aerosol particles is more than 0.25 μm,the path difference is approaches 4.6 cm with the mode radius increasing;when the millimeter and even sub-millimeter precision of satellite laser ranging is required,the path difference induced by time delay of atmospheric aerosol particles should be corrected.