The utility model discloses an insulating box device of an electrical tar precipitator. The insulating box device comprises an insulating box body, an inert gas pipeline, a hanging post and a high-pressure ceramic bottle, wherein the inert gas pipeline is communicated with the insulating box body; the hanging post is used for hanging an electrode device; the high-pressure ceramic bottle is arranged in the insulating box body; the hanging post is fixed on the high-pressure ceramic bottle; a self-operated type adjusting valve is arranged on the inert gas pipeline and is in a downstream type. The self-operated adjusting valve can be used for guaranteeing constant downstream pressure, so that pipe network pressure fluctuation around the high-pressure ceramic bottle is reduced. Therefore, the variable stress of the high-pressure ceramic bottle is reduced and the service life of the high-pressure ceramic bottle is prolonged.