The　dynamics　of　large　scale　circulating　fluidized　bed　(CFB)　boiler　power　plant　shows　the　behaves　of　large　time　delay,　complex　coupling　and　nonlinearities,　which　brings　difficulties　for　controller　design　to　improve　the　plant　performance.　This　paper　firstly　introduces　a　well-established　and　validated　nonlinear　model　of　a　300MWe　CFB　power　plant,　and　then　the　model　is　simplified　through　analysis　and　approximation　which　could　show　clearly　the　reason　of　difficulties　associated　with　controller　design.　It　is　found　that　the　coupling　and　nonlinearity　mainly　come　from　the　opening　of　main　steam　governing　valve　under　various　load　conditions,　and　it　is　hard　to　completely　decouple　the　multivariable　system.　To　avoid　the　difficulties　of　decoupling,　a　decentralized　PID　control　system　is　finally　proposed　to　control　the　unit　power　and　main　steam　pressure　after　nonlinear　model　transformation.　The　simulation　results　show　that　the　control　system　has　improved　dynamic　performance　in　load　reference　tracking　for　a　wide　range　of　load　changes,　and　also　good　disturbance　rejection　to　the　coal　quality　variation.　The　analysis　and　control　in　this　paper　provide　the　first　step　to　move　forward　for　future　control　quality　improvement　and　advanced　control　strategy　study.　©　2012　IEEE.