For the NC milling of aircraft girder parts, a plan for flexible, fast and multi-station clamping fixture is proposed. The mechanism composition, working principle and PLC control system of the flexible system are discussed in detail. Using the support plate and the baffle for positioning and pneumatic boosting mechanism is used to clamp. Sensor sensing, automatic positioning and clamping of workpiece is implemented by utilizing PLC controller. The corresponding control program is worked out and debugging success. The reference is provided for the application of multi-station flexible fixture system of aircraft structural parts in NC machining.