Existing　single-phase　ground　fault　mitigation　device　(SPGFMD)　is　usually　equipped　with　a　grounding　terminal,　but　the　resistance　of　the　grounding　grid　may　change　during　the　long-term　operation　of　the　power　system.　To　analyze　the　influence　of　the　grounding　grid　resistance　on　the　effectiveness　of　ground　fault　current　mitigation,　the　relationship　between　the　grounding　grid　resistance　and　the　residual　ground　fault　current　is　derived.　This　article　conducts　simulation　and　experiment　to　investigate　the　impact　of　various　grounding　grid　resistances　on　the　suppression　effect　of　ground　fault　current　under　different　ground　transition　resistance　circumstances.　The　critical　grounding　grid　resistance　that　affects　the　single-phase　ground　fault　current　mitigation　effect　has　been　identified,　offering　a　theoretical　foundation　for　the　on-site　evaluation　of　the　grounding　grid　status　of　SPGFMD.　The　influence　mechanism　of　grounding　grid　resistance　is　verified　by　the　simulation　and　experiment　results.　The　results　indicate　that　the　SPGFMD　with　current-based　method　can　withstand　a　certain　range　of　grounding　grid　resistance　variation　under　the　condition　of　a　single-phase　ground　fault　in　the　distribution　networks.　However,　the　effectiveness　of　ground　fault　current　mitigation　deteriorates　when　the　grounding　grid　resistance　exceeds　the　critical　threshold.　©　2025　John　Wiley　&　Sons　Ltd.