A simple and high precision method to measure the phase modulation characteristics of Liquid Crystal Spatial Light Modulator, namely, the relationship between phase and voltage(gray), is proposed. Using the Digital Wave Front Phase-shifting Interferometer, the phase difference from different voltage (gray) can be obtained directly from the interferometer, so it is easy to get the phase modulating characters of Liquid Crystal Spatial Light Modulator. The wavefront
correction has been realized by using the Liquid Crystal Spatial Light Modulator in adaptive Optics. The distorted wavefront can be tested in the Interferometer and be expressed by Zernike Polynomial, using the phase modulation character of Liquid Crystal Spatial Light Modulator, the corresponding gray picture can be set up. The conjugate wavefront can be obtained, and thus the correcting of the static distorted wavefront is completed and the effect is displayed as proved by the improvement of correlative parameters such as PV value, rms value and strehl ratio.