Because of the high hardness and high brittleness of ceramics, crack damage would be easy left in the finished surface. This will lower the reliability of ceramics parts. Studies show that Ultrasonic vibration Added Grinding (UAG) can greatly improve the surface quality, but how UAG to reduce the surface/subsurface damage isn’t very clear. To this purpose, the surface/subsurface crack mechanism of the ultrasonic vibration added grinding on ceramics was mainly analyzed in this article. The study shows that ultrasonic vibration can change the crack propagation direction to free surface, rather than propagate to the deep material which will happen in conventional grinding. And this will reduce the surface/subsurface crack defects.