This paper introduces the relationship between the moisture content in SF6 and the ambient temperature as well as the influences of moisture content in SF6 and materials of electrical apparatus on arc decomposite substances.The idea that a corresponding temperature ought to be stipulated for the allowable mos-ture content in SF6 standard and GIS standard is suggested.A method for determining the accumulated breaking current value is put
forward in terms of the measured arc decomposite substances.The measures for reducing the moisture in SF6 are suggested.