Compared to traditional metal materials, SiCp/Al composites has excellent physical and thermal properties. However, hole edge quality in the he holed drilling process becomes one of the main problems influencing the usability of the composites. In this paper, experimental study on drilling of SiCp/Al composites with diamond coated bits is carried out, the measured mechanical signals, the formation mechanisms and characteristics of hole edge defects are analyzed. It is shown that in the drilling process the process parameters have influence on the thrust force, and their effect are ordered as each drill depth, feed speed and spindle speed; the hole quality at the exit is better than that at the entrance; the defect formation mechanisms mainly include the fracture of Al matrix and the detachment of SiC particle. And the diamond coated bits are suitable for the drilling of SiCp/Al composites. It has reference value for the actual processing and application of SiCp/Al composites.