Beam transmission through atmospheric turbulence distorts the wavefront, and the dispersion effect of the transmission medium leads to differences in the wavefront distortion of beams with different wavelengths. In a dual-wavelength adaptive-optics system, the distortion difference is passed into the closed-loop correction system and finally produces a correction residual. Therefore, it is important to improve the correction accuracy by studying the transmission of beams of different wavelengths in the atmosphere and the change characteristics of the distortion difference.