The　thyristor　converter　valve　is　the　core　equipment　in　HVDC　(　high　voltage　direct　current)　transmission　system,　and　to　evaluate　its　reliability　in　special　electromagnetic　environment　is　quite　important.　In　this　paper,　based　on　the　existing　wideband　model　of　the　key　components　of　the　converter　valve,　the　modified　wideband　model　of　the　converter　valve　system　is　built　to　study　the　electrical　stress　of　the　converter　valve　under　the　special　electromagnetic　environment,　and　the　weak　parts　of　the　valve　are　further　studied.　The　influence　of　stray　parameters　in　the　valve　tower　on　the　electrical　stress　of　thyristors　is　mainly　studied.　The　results　show　that　it　is　practical　and　feasible　to　provide　basic　conditions　and　numerical　parameters　for　the　reliability　evaluation　of　thyristor　components.