The invention discloses an intermediate casing grinding clamping tool and grinding machining method. The tool comprises a mounting base for detachable connection with a mounting platform of grinding machining equipment, wherein a positioning supporting bearing surface is arranged on the mounting base and is used for being attached to a positioning supporting leaning surface of an intermediate casing to position and support the intermediate casing; three mounting positioning holes which are perpendicular to the positioning supporting bearing surface and communicating are formed in the positioning supporting bearing surface, the three mounting positioning holes are uniformly arranged at intervals along the circumferential direction of the positioning supporting bearing surface, and the threemounting positioning holes are correspondingly arranged corresponding to three of machining threaded holes of the intermediate casing supported and born on the positioning supporting bearing surface;and the tool further comprises three sets of connecting fasteners correspondingly arranged corresponding to the three mounting positioning holes, and the connecting fasteners are used for being arranged in the mounting positioning holes and the corresponding machining threaded holes from bottom to top by the bottom ends of the mounting positioning holes which are correspondingly arranged so as toconnected and fix the intermediate casing and the mounting base.