During　the　field　service　of　composite　insulators,　high　temperature　vulcanized　(HTV)　silicone　rubber　(SIR)　material　used　for　insulator＇s　sheath　and　sheds　is　gradually　aging,　and　thus　how　to　effectively　evaluate　its　aging　state　has　become　an　inevitable　issue.　In　this　paper,　artificially　corona-aged　and　naturally　site-aged　SIR　materials　are　employed　as　samples,　and　their　properties　such　as　hydrophobicity,　leakage　current,　trap　density/energy　level,　surface　microstructure　and　chemical　composition　are　investigated　for　comparative　study.　With　the　increasing　of　corona　aging　intensity,　the　contact　angle　of　SIR　samples　drops　gradually　and　recovers　more　slowly.　The　hydrophobicity　of　site-aged　insulators　also　declines,　from　HC1　for　2-year　service　to　HC5　for　15-year　service.　The　leakage　current　of　corona-aged　and　site-aged　samples　both　increase　with　aging,　which　indicates　that　aging　induces　the　increase　of　surface　conductivity　of　SIR　material.　The　peak　trap　density　of　corona-aged　and　site-aged　samples　increases　with　the　aging　duration　or　service　duration　remarkably.　The　changes　of　these　properties　are　attributed　to　the　changes　of　micro-structures　and　compositions　in　the　surface　layer　of　SIR.　The　scanning　electron　microscope　(SEM)　and　X-ray　photoelectron　spectroscopy　(XPS)　analysis　results　reflect　that　a　hardened　inorganic　silica-like　(SiO2)　layer　with　many　polar　chemical　groups　and　distributed　micro-pores　is　formed　on　the　surface　of　SIR　material　after　corona　aging.　Because　of　this　silica-like　layer,　the　hydrophobicity　decreases　while　surface　conductivity　and　trap　density　of　SIR　material　increases.　Besides　the　traditional　properties　like　hydrophobicity　and　surface　conductivity,　the　trap　density　is　expected　to　be　a　novel　parameter　for　effective　evaluation　of　aging　state　of　HTV　silicone　rubber　material.