Abstract: By using a beam model with linear non-uniform field profile in the x direction,the effect of beam non-uniformity and nonlinear thermal blooming in the optical beam control system on the far-field characteristics of high-power laser beams is studied.It is found that the non-uniformity of the initial beam affects the focusability and results in the astigmatism.The thermal blooming gives rise to a further decrease of the focusability and a further increase of the astigmatism.In addition,the peak intensity in the far-field is reduced and its position shifts away owing to the thermal blooming.