Aiming　at　the　problem　that　central　air-conditioning　system　can＇t　operation　stably　with　the　large　hysteresis　and　the　circuit　coupling　of　temperature　and　relative　humidity,　this　paper　presents　a　method　for　controlling　the　temperature　and　relative　humidity　of　air-conditioned　rooms　with　IMC-PID　controller　for　the　multivariable　system.　Air-conditioned　room　is　the　research　object　of　this　paper.　First,　get　the　temperature　and　relative　humidity　step　response　curve　of　air-conditioned　room,　in　order　to　establish　the　system　transfer　function　matrix.　Then　design　a　multivariable　decoupling　IMC　controller　of　this　system.　Finally,　to　make　the　controller　easy　to　use　in　practical　projects,　this　paper　integrates　the　IMC　controller　and　object　model　as　an　IMC-PID　controller.　MATLAB　simulation　results　show　that　this　method　can　solve　the　problem　that　temperature　and　relative　humidity　is　coupled.　In　the　case　of　model　mismatch,　the　controller　can　still　achieve　better　control　effect　than　conventional　PID　control.　©　2014　TCCT,　CAA.