In　this　paper,　the　degradation　characteristics　of　the　series　diodes　under　DC　high　voltage　operation　are　investigated.　Five　series　connected　diodes　are　operated　at　a　reverse　bias　voltage　of　1500V.　The　influence　of　the　DC　high　voltage　on　the　diode　parameters　is　analyzed　after　the　I-V　characteristic　test.　Finally,　an　annealing　experiment　is　performed　on　a　diode　that　stressed　under　DC　high　voltage.　The　results　show　that　the　high　voltage　will　introduce　defects　into　the　diodes,　which　leads　to　the　increases　of　the　recombination　current　and　the　ideality　factor.　The　degradation　degree　of　five　diodes　is　basically　the　same.　For　the　annealing　experiment,　the　recoverability　of　defects　can　be　observed.　©　2019　IEEE.