Abstract:According to the requirements that arc slot on fork shaft of transmission should have accurate relative position, series fork shaft could be placed on a set of fixture, multiple parts could be machined at the same time, a split type pneumatic milling fixture was designed. The fixture positioning way was that positioning block was used to limit fork shaft end face, dovetail cylindrical surface was beared fork shaft.So workpiece cylindrical surface were clamped pneumatically at more points. Through twostage strengthening institutions, the clamping force was increased. The vibration produced by alternating milling force was eliminated by flexible transmission torque. The cylinder size was chosen based on the calculation of cutting force. Finally group layout of the workpiece in the fixture was realized,so the production efficiency was improved and the processing quality was guaranteed.