Breakdown　and　surface　flashover　are　likely　to　occur　on　silicone　rubber　in　the　complex　operation　environments　of　electrical　system.　Firstly,　silicone　rubber　specimens　were　treated　by　ultraviolet　irradiation　in　vacuum　for　24　hours,　and　DC　breakdown　and　surface　flashover　characteristics　of　treated　and　untreated　specimens　were　tested.　Then,　the　activation　energy　and　relaxation　time　distribution　were　calculated　by　dielectric　relaxation　spectroscopy.　The　trap　characteristics　were　analyzed　by　surface　potential　decay.　Finally,　the　chemical　reaction　of　silicone　rubber　molecular　chains　was　characterized　using　infrared　spectroscopy.　The　results　indicate　that　the　molecular　chains　of　silicone　rubber　crosslink　via　ultraviolet　irradiation　in　vacuum,　the　activation　energy　of　dipolar　orientation　polarization　increases,　while　the　molecular　chain　relaxation　time　decreases　and　molecular　chain　dynamic　is　hindered,　which　can　improve　the　trap　level　and　suppress　the　charge　transport　process　of　silicone　rubber.　DC　breakdown　strength　and　surface　flashover　voltage　will　increase　by　2.38%　and　8.79%,　respectively.　The　molecular　chain　dynamic　and　charge　transport　process　of　silicone　rubber,　which　is　irradiated　by　ultraviolet　in　vacuum　of　which　pressure　is　lower　than　5×10-4　Pa　for　24　h,　are　suppressed,　thus　the　DC　breakdown　and　surface　flashover　characteristics　will　be　enhanced　efficiently.　The　results　can　provide　references　for　solving　breakdown　and　surface　flashover　in　silicone　rubbers.　©　2019,　High　Voltage　Engineering　Editorial　Department　of　CEPRI.　All　right　reserved.