In　this　paper,　a　composite　insulator　with　seven　years　running　history　at　power　grid　was　taken　into　account.　At　first,　an　electric　field　was　computed　through　finite　elements　method　and　electric　field　difference　at　different　shed　was　compared.　Secondly,　through　SEM　photos　of　silastic　sections　from　different　sheds,　microcosmic　structure　character　of　silastic　aging　under　electric　and　ultraviolet　effect　was　analyzed;　through　contrasting　microcosmic　structure　of　side　surface　with　top　and　bottom　surface　of　shed,　the　rules　of　electric　aging　and　electric　erosion　was　studied;　through　energy　spectrum　analysis,　the　possibility　of　surface　contamination　moving　into　inner　of　silastic　was　studied.　The　results　gotten　from　this　paper　are　positive　and　helpful　for　advanced　aging　studying　of　composite　insulator　and　optimization　design　of　insulator　for　anti-aging.