The aspheric surfaces are measured by an infrared interferometer with a long working wavelength (λ=10.6 μm). By using the phase-shifting infrared interferometer, the wavefront aberration between aspheric wavefront and reference spherical wavefront is measured. Then, the theoretical value of the wavefront aberration is computed based on the aspheric surface equation. Finally, the surface deviation of tested asphere is obtained by subtraction of the theoretical wavefront aberration from the measured one. Experimental results show that the measured wavefront aberration is 8.64 μm(PV), which is close to the theoretical wavefront aberration(8.11 μm) .Furthermore, the aspheric surface deviation is 1.20 μm(PV). In order to verify the accuracy of this method, the same asphere is measured by using a Computer Generated Hologram(CGH) method,and the results show that the two methods are coincident well. It is concluded that the method has advantages of easy operation and good flexibility,and can meet the measurement requirement of the aspheric surface manufacture.