This artical carried out a comparative study between helical milling and drilling of C/SiC composite ma- terials. The cutting force,cutting temperature and hole quality of helical milling and drilling were measured under the same working efficiency. The results indicate that the axial force of PCD helical milling is less than PCD drilling and ocuppies nearly 56.9% of PCD drilling. The hole roughness and tolerance of helical milling are less than drilling. The cutting temperature of PCD drilling is less than helical milling and ccupies 58.7% of helical milling. In addition, the cutting heat of helical milling has a small influence on C/SiC composite materials and PCD tools.