Type GW5 series outdoor high voltage disconnector (hereinafter referred disconnector) is widely used in power plant, substation and mine industrial enterprises with such features as good-looking appearance, small land occupation, multiple types of installation and is well received by the users. With rapid development of electric industry, higher requirement on various types of high voltage apparatus is raised and old type of GW5 disconnector can not meet the need. For this situation, we conduct modification design based on original type in accordance with existing national and international standards as well as problems encountered by the disconnector in use. Both electrical and mechanical performance of the disconnector after modification has improved a lot and the product has completely reached requirement of National standar GB1985 and its first revision and international standards IEC129, IEC694 as well.