The　converter　valve　is　the　core　equipment　in　the　HVDC　transmission　power　system　and　the　thyristor　level　is　the　basic　unit　of　HVDC　converter　valve,　its　performance　has　a　direct　effect　on　the　reliability,　stability　and　efficiency　of　the　whole　power　system.　Thus,　each　thyristor　level　in　the　converter　valve　needs　to　be　test　routinely　during　the　maintenance　period　of　the　electric　equipment　in　order　to　grasp　the　state　of　the　converter　valve　equipment.　Currently　there　is　no　specific　test　scheme　for　the　thyristor　level　with　thyristor　control　unit　(TCU).　Therefore,　it　is　particularly　urgent　to　study　the　synthetic　test　technology　of　the　thyristor　level　with　TCU　in　the　HVDC　converter　valve.　In　this　paper,　the　synthetic　test　principle,　content　and　methods　for　the　thyristor　level　with　TCU　are　presented　based　on　the　analysis　of　the　thyristor　level　electrical　principles　and　the　IEC　60700-1-2008　standard　in　order　to　offer　technical　support　for　the　operation　and　maintenance　of　the　HVDC　converter　valve.　In　general,　the　reverse　recovery　period　of　thyristor　level　is　the　most　vulnerable　stage　of　thyristor　operation　process,　so　a　transient　high-voltage　pulse　is　applied　to　the　thyristor　level　during　its　reverse　recovery　period　in　order　to　test　the　damage　characteristics　of　thyristor　level.　Then,　the　synthetic　test　system　for　the　thyristor　level　is　designed　and　applied　to　the　converter　valve　test　of　+/-800kV　HVDC　transmission　power　project,　and　the　practical　test　result　verifies　the　reasonability　and　validity　of　the　proposed　synthetic　test　technology,　which　meets　the　need　of　engineering　application.