The invention relates to an isolating and grounding switch mechanism and a gas-insulated metal-enclosed switchgear. The isolating and grounding switch mechanism comprises a housing, an isolating switch and a grounding switch. The isolating switch comprises an isolating switch movable contact and an isolating switch static contact, wherein the isolating switch movable contact and the isolating switch static contact are axially arranged in parallel. The grounding switch comprises a grounding switch movable contact and a grounding switch static contact. A transformer connection terminal, an external connection terminal used for accessing a main loop to a conductive structure, a guide contact holder and a connection contact holder are arranged inside the housing, wherein the guide contact holder and the connection contact holder are horizontally arranged side by side along the axial direction. The transformer connection terminal is arranged on the guide contact holder. The isolating switch static contact is arranged on the connection contact holder and is oriented towards the guide contact holder. The external connection terminal is arranged on the connection contact holder and is used for axially accessing the main loop to the conductive structure. The isolating switch movable contact is axially guided to pass through the guide contact holder and is provided with a closing station in contact cooperation with the connection contact holder. In this way, the problem in the prior art that an existing isolating and grounding switch mechanism is large in occupation space in the vertical direction and poor in part durability can be solved.