Surface　discharge　of　insulating　materials　is　the　main　form　of　insulation　failure　of　electrical　equipment　under　special　operating　environment　such　as　high　humidity,　high　pollution　and　easy　condensation.　Therefore,　it　is　of　great　significance　to　study　the　discharge　initiation　characteristics　of　wet　insulated　material　surface　to　improve　the　operation　reliability　of　electrical　equipment.　In　this　paper,　the　discharge　initiation　characteristics　of　insulating　materials　under　the　action　of　condensation　and　pollution　were　studied.　Firstly,　COMSOL　software　was　used　to　construct　a　single　droplet　model　under　the　action　of　a　flat　electrode,　and　FEM　was　used　to　calculate　the　electric　field　distribution　on　and　around　the　surface.　Secondly,　a　method　for　predicting　the　initial　voltage　of　surface　discharge　of　wet　insulation　materials　based　on　photoionization　criterion　is　proposed.　Finally,　the　corona　test　was　carried　out　on　the　surface　of　the　wet　epoxy　resin　plate,　and　the　corresponding　corona　voltage　was　calculated　by　the　leakage　current　method.　The　results　show　that　the　error　between　the　experimental　value　and　the　simulation　value　is　small,　which　verifies　the　validity　of　the　method　for　predicting　the　negative　polarity　DC　corona　initial　voltage.　©　2023,　The　Author(s),　under　exclusive　license　to　Springer　Nature　Singapore　Pte　Ltd.