The invention provides a multi-station automatic fixture for an airplane long beam, which comprises a fixture body, a positioning device, a clamping device, a detection device, a station conversion device and a control device, wherein the positioning device comprises two inner support plates, two inner baffles, an outer baffle and an end baffle; the clamping device comprises a clamping cylinder, a pressing plate, two cylinder bottom plates, an end cylinder bottom plate and an air pump; the detection device comprises a photoelectric sensor and a pressure sensor; the station conversion device comprises a cylinder, a workpiece chuck, a crankshaft rotating mechanism, a base and a sliding support; the positioning device is connected with the clamping device and the station conversion device by the fixture body; the control device is connected with the clamping device and the detection device; and the detection device is connected with the fixture body, the positioning device, the workpiece conversion device and the clamping device. The multi-station automatic fixture is applicable to airplane long beams of different sizes, can improve the flexibility of the fixture, realizes multi-station numerical control milling machining of automatic clamping and automatic detecting of the airplane long beam, and can improve the automation degree.