In this paper, the beam quality optimization of an elliptical Gaussian beam under wind-dominated thermal blooming is studied analytically and numerically. The expression of distortion parameter of an elliptical Gaussian beam propagating in the atmosphere is derived, and its correctness is proved. Due to the astigmatism of an elliptical Gaussian beam, the influence of atmospheric thermal blooming on its propagation depends on the wind direction. Thermal blooming can be weakened by making the short axis of a focused EGB along the general wind direction. In the atmosphere, as the beam width in the windward direction of the source plane is large (the same spot area), the thermal blooming effect on the EGB is weak, which results in a better symmetrical spot and energy focus ability at the target, i.e. better beam quality at the target. The time required to achieve steady-state thermal blooming for a focused elliptical Gaussian beam is proportional to the beam width along the wind direction in the source plane.