The burrs and the delamination defects are easy to be generated during the drilling of carbon fiber reinforced plastics (CFRP). In this paper, two types of new drills with the similar structures are designed and manufactured by employing the tungsten carbide material and the PCD material. The defects formations and the variations of the thrust forces as well as the defects under different drilling conditions are investigated. The results show that the drilling processes of these two structures can be obviously distinguished eight stages, according to the time-variable thrust forces. Both of the thrust forces in the drilling period of reamer edge and in the drilling period of the 2^nd counterboring edge are minimal. Additionally, the 2^nd counterboring edges Ⅳ of the two structures play an extremely crucial role for reducing the defects. The drilling effect of the linear drill structure is better than that of the arc-shaped drill structure, but the ability to restrain the burrs may be weakened with the increasing of the spindle speed and the feed speed. Compared to the carbide drill bits, the PCD drill bits have the absolute advantage for suppressing the defects.