The main contents of this design are the compilation of machining process specification of machine body, the design of rough milling fixture for top and bottom surface, and the design of fine boring fixture for cylinder hole. The factors affecting the machining quality of typical working procedures of engine block and the main countermeasures are analyzed and studied. The formulation of processing technology regulations should conform to the production situation, and the production procedure should be mass production. The fixture design should meet the processing technical requirements, and the operation is convenient and safe.