This research aims to investigate the surface/subsurface damage of silicon wafer induced by precision diamond grinding. Effort has been made to clarify the effect of spark out on surface integrity of the obtained surface. It is found that the damaged layer of precision ground silicon wafer are typically composed of defects such as amorphous layer, dislocation and micro-cracks. The machining parameters have profound effect on the extent and distribution of these defects. Based on the results of this study, surface generated by applying moderate spark out (5-6 revolutions) can effectively reduce the thickness of the damaged layer. Very little improvement can be obtained when spark out are pushed to 12-24 revolutions. 12" silicon wafers of Ra better than 11 nm and 5 nm and thickness of the damaged layer smaller than 180nm and 70nm are obtained by rough and fine grinding respectively in this research.