The principle and the method of aspheric surface measurement by infrared interferometer is introduced. The axial deviation between aspheric surface and standard fit spherical surface is calculated

and the relationship between this deviation and the wavefront aberration is deduced. The aspheric surfaces with large asphericity can be measured by the use of infrared interferometer with the advantage of long working wavelength (λ=10.6μm). The wavefront aberrations of the tested aspheric surface and the standard fit spherical surface are measured

then the measured wavefront aberration and the calculated wavefront aberration are compared

and the surface quality of aspheric surface is obtained. The result shows the surface deviation is 1.20μm(PV). The method has advanges of easy operation

low cost

and good generality.