It is an important part to measure the distortion and divergence of laser pulse wavefront in ICF (Inertial Confinement Fusion). The paper described a radial shearing interference system with spatial phase modulation. It can be used for testing the wavefront distortion and control the beam quality. Because it is a cyclical common path interference system and no any reference surface, both radial sheared wavefront are formed by a Galilean optical system. A 512x512 pixels CCD camera recorded interference pattern. The wavefront reconstructed is finished by means of optical information processing method and software. The software procedure consists of the Fourier transform, shifting frequency, inverse Fourier transform, unwrapping 2π and wave iterations reconstructed. The interferometer has been used for testing a wavefront distortion of laser pulse with 1064nm near-infrared wavelength and 10 ns pulse time width. Results of the pulse wavefront quality and distribution of energy can be displayed by a perfect software procedure. Diameter of beam be measured is up to 150 mm. The testing precision of RMS(root-mean-square) is better than 1/15 wavelength.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.