Subsynchronous　control　interaction　(SSCI)　in　DFIG-based　wind　farms　has　attracted　intensive　attention　from　the　academia.　In　order　to　further　study　the　mechanism　of　SSCI,　this　paper　carries　out　equivalent　circuit　modeling.　Firstly,　based　on　the　numerical　equivalent　circuit　of　PI　control　unit,　the　equivalent　model　of　RSC　is　built.　Furthermore,　the　RSC　model　is　simplified　by　PI　parameter　sensitivity　analysis,　and　the　impedance-frequency　curve　of　the　target　system　is　obtained　by　frequency　scanning.　Then,　the　mechanism　and　influencing　factors　of　SSCI　are　studied　based　on　the　equivalent　circuit　model,　which　are　verified　by　simulation　analysis　finally.　©　2019　IEEE.