A method which adopted plane-parallel plate as active optics element is proposed to compensate the astigmatism because of non-uniformed illumination in projection objective. The supporting structure is designed and analyzed for the plane-parallel plate with Φ140 mm diameter. The key parameters of supporting structure, the thickness of lens and the driving force are analyzed to receive the influence rules to the surface quality. The results indicate that the influence of the key parameter and driving force on the surface quality seems to be linearity, and the influence of lens thickness on the surface quality seems to be exponential. The figure is received by changing the value of driving force. The results indicate that high order aberration which the supporting structure brings is negligible when compensating. The resolution of astigmatism compensation is 2 nm. The designed and analyzed results provide reference for selecting of active optics lens, designing of supporting structure and experiment.