In the semiconductor intersatellite communication system, how to test the laser beams′ quality is difficult. In order to solve this problem, a basal principle of the white light lateral double-shearing interferometer is introduced firstly, and then measuring the semiconductor laser beam′s wavefront which is near the diffraction-limited by the interferometer is reported, and the formula of calculating the beam′s divergence is deduced according to the Fraunhofer diffraction. A 0.2λ wavefront error is gained experimentally. Corresponding to the wavefront error, the divergence angle is only 64.8 μrad, which indicates the beam is near the diffraction-limited. The result shows that the interferometer has high precision and wide practicability.