Polycrystalline diamond (PCD) end mill was applied during the trimming experiment of CFRP by introducing the definition of workpiece inclined angle. The milling forces were recoded and different types of machining defects were observed at the same time. The influences of carbon fiber angle, workpiece inclined angle and feed rate on the types and evolution of machining defects were analyzed. The results show that the main machining defect is avulsion of carbon fiber bundles with small amount of chipping, burrs and delamination. The feed rate of cutter is the most significant factor on the occurrence of machining defects especially on the avulsion of fiber bundles. The cutting force perpendicular to the laminate panel has the direct influence on the occurrence and evolution of defects.