In　DC　withstand　test　and　polarity　reversal　test,　there　would　be　space　charge　at　interfaces　of　oil-paper　insulation　in　converter　transformer,　which　may　excite　partial　discharge　in　subsequent　tests.　So　it　is　important　to　study　distribution　of　space　charge　in　converter　transformer.　This　paper　simulated　the　distribution　of　space　charge　in　a　+/-　500kV　converter　transformer　during　DC　withstand　test,　polarity　reversal　test　and　earth　with　finite　element　method.　It　was　studied　that　the　influences　of　changing　resistivities　of　oil　and　paper　on　space　charge　distribution　in　+/-　500kV　converter　transformer.　Based　on　the　calculation　of　space　charge,　the　study　indicates　that　the　ratio　of　resistivities　of　oil　and　paper　has　a　great　influence　on　distribution　and　release　rate　of　space　charge　in　+/-　500kV　converter　transformer.