Abstract: A novel aspheric surface testing method using part-compensating lens is presented. Specific design requirements and design methods of part-compensating lens are given. The design requirements are applied in the optimization design of the part-compensating lens to three kinds of aspheric surfaces, and it is proved that the structure of part-compensating lens is much simpler than that of null compensator. Analysis is made about the asphericity compensation range of each part-compensating lens. The results demonstrate that aspheric surfaces with different relative aperture and asphericity can be compensated by part-compensating lens which is simple and easily fabricated. The measurement precision can reach λ/10.