The　wet　flue　gas　desulfurization　(WFGD)　process　is　a　complex　controlled　system　with　nonlinear　and　time-varying　characteristics.　There　are　a　variety　of　external　disturbances　in　the　desulfurization　process,　which　can　easily　cause　a　jump　in　system　parameters　and　even　structure.　In　response　to　this　problem,　a　model-free　adaptive　control　scheme　based　on　a　switching　mechanism　is　proposed,　and　the　convergence　analysis　is　given.　In　the　scheme,　firstly,　the　operating　conditions　of　the　WFGD　system　are　divided　into　n　kinds　based　on　multiple　external　disturbances,　and　the　mathematical　models　of　the　multi-input　multi-output　WFGD　system　under　different　operating　conditions　are　established.　Then　the　MFA　controllers　of　the　WFGD　system　under　multiple　operating　conditions　are　established,　respectively.　Finally,　a　switching　index　function　is　designed　to　switch　the　controller　of　the　WFGD　system　according　to　different　operating　conditions,　so　that　the　desulfurization　system　is　always　controlled　by　the　most　appropriate　controller.　In　the　simulation　experiment,　according　to　the　actual　data　of　the　WFGD　system　of　a　1000　MW　coal-fired　power　station　in　Beijing,　the　modeling　test　and　algorithm　simulation　of　the　WFGD　system　under　three　operating　conditions　are　carried　out.　The　simulation　results　show　that　this　method　can　effectively　reduce　the　transient　error　of　the　WFGD　system　output　and　improve　the　desulfurization　effect.