Abstract: The principle of measuring normal deformation of the surface of friction welding joint is analyzed. When the experimental system meets some conditions, the interferometric fringe obtained from double-exposure hologram reflects the amplitude of normal deformation. In experiment, a Q-switched ruby laser is used as light source, and a double exposure hologram of friction welding joint is obtained. In this paper, the holographic interferometric fringe is collected through a CCD image process system and stored into computer. After using computer to process these data, the amplitude of normal deformation of the surface of friction welding joint is obtained.