To　meet　the　demand　of　developing　compatible　and　energy-efficient　flexible　spintronics,　voltage　manipulation　of　magnetism　on　soft　substrates　is　in　demand.　Here,　a　voltage　tunable　flexible　field-effect　transistor　structure　by　ionic　gel　(IG)　gating　in　perpendicular　synthetic　anti-ferromagnetic　nanostructure　is　demonstrated.　As　a　result,　the　interlayer　Ruderman-Kittel-Kasuya-Yosida　(RKKY)　interaction　can　be　tuned　electrically　at　room　temperature.　With　a　circuit　gating　voltage,　anti-ferromagnetic　(AFM)　ordering　is　enhanced　or　converted　into　an　AFM-ferromagnetic　(FM)　intermediate　state,　accompanying　with　the　dynamic　domain　switching.　This　IG　gating　process　can　be　repeated　stably　at　different　curvatures,　confirming　an　excellent　mechanical　property.　The　IG-induced　modification　of　interlayer　exchange　coupling　is　related　to　the　change　of　Fermi　level　aroused　by　the　disturbance　of　itinerant　electrons.　The　voltage　modulation　of　RKKY　interaction　with　excellent　flexibility　proposes　an　application　potential　for　wearable　spintronic　devices　with　energy　efficiency　and　ultralow　operation　voltage.