Combustion chamber casing is a key component of aeroengine, because of its poor rigidity, severe chattering occurs during milling, which seriously affects the surface quality and processing efficiency of the casing, and the existence of geometric nonlinear problems in the machining process makes it difficult to predict machining vibration. Therefore, it is of great significance to study the vibration law of thin-walled casing and reduce machining vibration. Aiming at the problem of vibration control of thin-walled casing, this paper proposes a new type of gasbag-rubber damping flexible fixture, which differ from the ordinary rigid fixture, this fixture has adjustable clamping force and good vibration damping ability. The key factors affecting the vibration response of the thin-walled casing are studied through establishing an equivalent dynamic model of the workpiece-fixture system. The research results show that the gasbag-rubber damping flexible fixture can effectively provide support stiffness, which is beneficial to reduce the vibration of the workpiece during processing; According to the actual thickness of different workpieces, the appropriate gasbag pressure is recommended to give play to the vibration damping performance of the fixture; It is recommended that the thickness of the rubber damping block in practice is 8~12mm. The research work in this paper has important guiding significance for the design and use of the gasbag-rubber damping flexible fixture, and provides an effective theoretical prediction for the vibration of the thin-walled casing.