Due to the special properties of asphere lens.the testing of it is more difficult than that of spherical lens.In this paper,the development of a new method using the liquid crystal spatial light modulator (SLM) to measure the accuracy of an aspheric surface is presented.The surface form was measured using a new component as the compensator lens in conjunction to provide an interferogram representing the aspheric form deviation from the nominal.Interferograms are decoded using a spatial- carrier phase-shifting technique.The interferometric data is compared to data obtained using a contact stylus profilometer.The system can be mounted over a polishing machine and used for on-line testing of aspheric mirror surfaces.