A model of the modified Rytov method is derived based on the wander in the original theory, this method takes into account the outer scale and the impact of multiple scattering on the wander, wander formula for certain improvements, and more with the experimental data. Analysis all kinds of factors of the wander variance. The results show that the outer scale of turbulence, turbulence intensity and beam radius of the wander play a major role, whereas the beam does not influence the wavelength of the beam wander variance.