Electric　field　(E-field)　modulation　of　perpendicular　magnetic　anisotropy　(PMA)　switching,　in　an　energy-efficient　manner,　is　of　great　potential　to　realize　magnetoelectric　(ME)　memories　and　other　ME　devices.　Voltage　control　of　the　spin-reorientation　transition　(SRT)　that　allows　the　magnetic　moment　rotating　between　the　out-of-plane　and　the　in-plane　direction　is　thereby　crucial.　In　this　work,　a　remarkable　magnetic　anisotropy　field　change　up　to　1572　Oe　is　achieved　under　a　small　operation　voltage　of　4　V　through　ionic　liquid　(IL)　gating　control　of　SRT　in　Au/[DEME](+)[TFSI](-)/Pt/(Co/Pt)(2)/Ta　capacitor　heterostructures　at　room　temperature,　corresponding　to　a　large　ME　coefficient　of　378　Oe　V-1.　As　revealed　by　both　ferromagnetic　resonance　measurements　and　magnetic　domain　evolution　observation,　the　magnetization　can　be　switched　stably　and　reversibly　between　the　out-of-plane　and　in-plane　directions　via　IL　gating.　The　key　mechanism,　revealed　by　the　first-principles　calculation,　is　that　the　IL　gating　process　influences　the　interfacial　spin-orbital　coupling　as　well　as　net　Rashba　magnetic　field　between　the　Co　and　Pt　layers,　resulting　in　the　modulation　of　the　SRT　and　in-plane/out-of-plane　magnetization　switching.　This　work　demonstrates　a　unique　IL-gated　PMA　with　large　ME　tunability　and　paves　a　way　toward　IL　gating　spintronic/electronic　devices　such　as　voltage　tunable　PMA　memories.