This application relates to a pre-assembly / disassembly device for large synchronous chain plates, comprising a steel frame with two steel beams slidably connected to it. Each steel beam is equipped with a gripper, and multiple grippers are arranged along the length of the steel beams. A driving component is provided between the two steel beams to move them closer together or further apart. This application effectively reduces the tension between the chain shaft and the chain, thereby improving the pre-assembly / disassembly preparation efficiency for large synchronous chain plates.