To decrease the influence of the positioning error caused by multiple bearing and clamping on the machining accuracy of the part, the processing technology of the connecting rod parts was analyzed, the design concept of the process centralized automatic fixture was proposed. The design concept included that the design datum of parts needed not be processed was taken as the positioning datum, the gas source of the CNC machine tool was taken as the power, and PMC was taken as the control device. The CNC machine tool automatic fixture for connecting rod parts based on PMC was completed by designing the fixture structure, pneumatic system and control system. It has simple structure, accurate positioning, reliable clamping and good stability.Experiments show that the accuracy of the surface position of connecting rod parts is improved to a certain extent by using this fixture to process connecting rod parts.