The invention discloses a solid insulation ring main unit, comprising a high-voltage switch unit; the high-voltage switch unit comprises a vacuum arc-extinguishing chamber and an isolation grounding switch device comprising an insulation cavity body; a line outlet end, a grounding end and a line inlet end electrically connected with a conductive rod are arranged on the insulation cavity body; a vacuum switch tube for grounding is fixedly arranged inside or outside the insulation cavity body; the static contact of the vacuum switch tube for grounding is electrically connected with the grounding end while the movable contact is provided with a grounding wiring part; the movable contact of the vacuum switch tube for grounding is in transmission connection with a grounding operative mechanism; an isolation disconnecting link is arranged in the insulation cavity body; one end of the isolation disconnecting link is a hinging end hinged to the line outlet end while the other end is a contact end; and a driving mechanism is connected onto the isolation disconnecting link in a transmission way. The isolation grounding switch is positioned in different work conditions by controlling the swinging of the isolation disconnecting link and the connecting/disconnecting states of the static and movable contacts in the vacuum switch tube.