The utility model discloses a support earthing device of GIS bus, which comprises GIS bus shell bodies, wherein the shell bodies are connected with a flange and an earth lead. The device is characterized in that one of the shell bodies is connected the lower portion of the back surface of the flange and is connected with a support with an earthing terminal through a flange support, the other shellbody is connected with the earthing terminal which is located on the lowest point of the back surface of the flange and is fixed on an earth lead connecting support, and the earthing terminal is connected with an earth screen of the device foundation through an earth screen earthing lead. The device omits welding supporting legs and earthing blocks on the welding supporting legs in the designed structure, and enables the manufacturing of products to be simple, uses fewer materials, reduces the cost, has beautiful appearance, and is convenient to install under the precondition of guaranteeingthe performances.