Abstract: In order to obtain light alloy(aluminum, magnesium alloy, etc.)clad plates with excellent properties, the vacuum friction stir welding machine was developed, which effectively solved the problem of vacuum billet making caused by the poor electron beam welding performance of the light alloy.The structure and working principle of the machine were described in detail.The corresponding composition systems included mechanical system, control system, vacuum system, cooling system and pneumatic system.The vacuum system, cooling system and pneumatic system were controlled by PLC to complete the vacuum pumping process.The plane and curved surface welding was realized by CNC controlled servo drive system.The welding test of 7050 aluminum alloy was carried out with the machine.The results showed that the mechanical properties and surface flatness of the welded joint were the best when the rotating speed was 600 r/min and the welding speed was 100 mm/min.The development of this machine provides a necessary tool and means for investigating the preparation process, interfacial microstructure evolution, and bonding mechanism of light alloy clad plates.Highlights:(1)A friction stir welding machine for welding aluminum, magnesium and other light alloys in vacuum was developed, and the optimum welding parameters for 7050 aluminum alloy were obtained.(2)The machine provided a good test platform for the development of light alloy clad plates.