Nuclear large cylinder is one of the basic components of nuclear power generating units, compound angle inclined deep hole processing is key and difficulty of cylinder block machining. Through analyzing processing difficulty and processing status of composite angle deep hole, the machining method, cutting tool, clamping, cooling and lubrication were researched emphatically. Special fixture and spade drills were combined to successfully complete processing of composite angle deep hole.The product meets the processing requirements.So the processing technical problems of nuclear power cylinder composite angle inclined deep hole is solved fundamentally.