Abstract: One of the primary challenges in developing higher-power laser systems is the aero-optical thermal blooming effect that occurs during laser beam propagation through the inner channel. This effect refers to the phase distortion and degradation of far-field beam quality due to the uneven changes in temperature and density of the flow field within the channel as the gas medium absorbs the laser's energy. At present, there is still a lack of high-accuracy and systematic coupling numerical simulation method for the study of the thermal effect. Thermal blooming effect is calculated and analyzed based on the research framework of the coupling of light field and flow field in this paper. Difference between the geometric ray tracing method and the linear integration method in calculating the wavefront distortion is compared in this paper, which proves that the approximate treatment of beam’s rectilinear propagation can be used to deal with the case discussed in this paper. The wavefront distortion is fitted by Zernike polynomial, and the distortion level and its influence on far-field intensity characteristics is analyzed in combination with adaptive optical correction. The results show that wavefront distortion caused by thermal effect within 0.5 seconds without adaptive optical correction is serious, and wavefront distortion increases approximately linearly with time. Ensure that the ratio of pipe radius to beam radius is greater than 1.5 can effectively reduce the thermal blooming effect. By using adaptive optical correction, wavefront distortion can be reduced by about 70%. Due to the phase modulation effect of the wavefront distortion in the inner channel and the diffraction effect of the far-field transmission, there are serious problems of light intensity reduction and spot diffusion after a considerably long distance of far-field transmission without improvement measures. Through the adaptive optical correction, far field beam quality can be improved significantly. Therefore, controlling the geometry parameters of the laser transmission channel and using adaptive optics correction are effective ways to reduce the thermal effect.