High strength carbon fiber reinforced polymer (CFRP) with unidirectional laminate structure has gradually developed into major material in load bearing components in aerospace， and the cutting demand of CFRP is increasing. Because of the significant anisotropy， CFRP laminates highly tend to produce defects and are typical difficult to machine materials. Orthogonal cutting experiments on T800 high strength CFRP unidirectional laminates are conducted to study the variation of cutting force， torque and cutting temperature with different fiber orientations. Based on the drilling experiments with brad point drill and multifacet drill， the effects of cutting force， torque and cutting temperature on defect forming process are discussed， and SEM topography of hole wall surface with typical defects is given. Through analyzing the wall surface of drilling holes， defect formation mechanism under different drilling processes is given. 