To solve the problem of machining defects such as burrs and chipping during machining of carbon fiber reinforced plastics (CFRP), a computing method of the length of carbon fiber cut by per tooth was proposed based on fiber cutting angle. This method explained the mechanism and regularity of burrs. The results of the computation and experiment showed that the length of carbon fiber cut by per tooth and the number of total cutting edges acted on the same carbon fiber were determined by the fiber cutting angle. With the increase of fiber cutting angle, the length of carbon fiber cut by per tooth increased and the frequency of the cutting action between the fiber and cutting edge decreased. The reason for the occurrence of burrs is that the actual bending radius is larger than the minimum bending radius. The carbon fiber tended to be bent instead of being fractured. Also chipping could be found within the fiber cutting angle range of 0~90°. Burr was observed when the fiber cutting angle was in the range of 90°~180° during the verification slotting experiment. And the length of burr increased with the increase of fiber cutting angle.