The principle of mean curvature flow is illustrated. An optimizing method using mean curvature flow is proposed which can reduce the undesirable astigmatism in some regions of the progressive addition lens surface while retaining desirable optical features of the progressive lenses. It is presented that the more the surface of the progressive lens becomes closer to spherical by the process of mean curvature flow, the more the astigmatism is smaller. The optimizing algorithm and an example are given out. An initial designed progressive addition lens and an optimized lens by this method are manufactured and tested. Compared with the original lens, the optimized lens has smaller maximum astigmatism value and larger clear region on the intermediate zone and the distance-vision zone.