This paper describes a method to obtain the local removal rate for the polishing process of the small aspherical lens die using a spherical tool. When the small spherical polishing tool traverses an aspherical surface, non-uniform polishing area and local removal rate are locally generated around the contacting points according to the curvature change of an aspherical surface. Therefore, an aspherical surface is divided into multiple patches and the local removal rate on the patches is calculated semi-empirically from the Preston equation. Formation of the elliptical polishing area is confirmed experimentally and the Preston coefficient is calculated from the central removal depth and dwell time that has a linear relation with the local removal depth. Finally, using the equivalent radius of two contact bodies, the curvature effect of an aspherical surface on the polishing area is explained. (C) 2001 Elsevier Science B.V. All rights reserved.