The radial sheering interference technique is used to measure the laser wave-front. In the system, the near field and far field wave-front of the laser beam of large caliber are measured respectively. Many evaluation parameters of the laser wave-front can be obtained, such as scattering angle, M2 of the laser beam, peak-to-peak-value (PPV), strehl value et. al. The interferogram is acquired by CCD camera, pretreated by high-capability computer and then used to reconstruct the wave surface. Mathematical principle to reconstruct the wave-front is expatiated in the paper. The interference system can be adjusted easily and operate real-time during the experiment.