Common-box and common-air-chamber type GIS main cylinder and GIS

The invention relates to the technical field of high-voltage power transmission, in particular to a common-box common-air-chamber type GIS main cylinder and a GIS. The GIS comprises a GIS shell, a circuit breaker and an isolation grounding switch, the circuit breaker and the isolation grounding switch are installed in the GIS shell, the GIS shell comprises a main cylinder, the main cylinder is of an integrated structure and comprises a main cylinder section used for installing the circuit breaker and branch cylinder sections used for installing the isolation grounding switch, the number of the branch cylinder sections is at least two, and the branch cylinder sections are connected to the radial direction of the main cylinder section. The branch cylinder section is communicated with the inner cavity of the main cylinder section, the inner wall of the branch cylinder section is provided with an insulating support for fixedly supporting an isolating switch movable contact seat, and the cylinder wall of the branc