With developing of shortwave optics and more requirement of lofty precision optical machine, the processing and measurement of fine precision surface are becoming important. But in common interferometry, the metrical precision of spherical surface mainly Sepends on the precision of reference surface. So an absolute calibration method has been described (Jensen in 1973) that is ideally suited to a real-time interferometer to wipe off all additive aberration. Based on the absolute calibration theory a method which rotates the wavefront by using Zernike polynomials is put forward, and detailed projects are given. We get fine precision by measuring surface of small protruding spherical surface with precision above λ/37, and break the localization of standard lens which λ/20 is the best. The method can be used to get fine metrical precision of spherical surface.