The invention provides a bus duct volume varying connection structure which comprises a large current bus duct, a small current bus duct and a connector, wherein a busbar of the large current bus ductand a busbar of the small current bus duct are respectively inserted into and fixed on the two ends of the connector, the connector comprises an upper cover plate, a lower cover plate, a plurality ofinsulating partition plates, a double-end bolt and a first nut; and two first insulating baffles are arranged on the upper end face of each insulating partition plate. A first insulating pressing block and a second insulating pressing block are arranged on one first insulating baffle, the first insulating pressing block and the second insulating pressing block are bonded and fixed on the inner wall of a first insulating baffle, and a third insulating pressing block and a fourth insulating pressing block are arranged on the other first insulating baffle. The fourth insulating pressing block and the second insulating pressing block are arranged correspondingly and are movably arranged on the inner wall of the second insulating baffle. The bus duct volume varying connection structure is simple and compact in structure, flexible and convenient to install and low in machining cost.