This work present the various methods for the design of controllers for a Multiple-input Multiple-output system (MIMO). Distillation column dynamics from the literature are considered for the controller design. The decentralized controller design, and decoupling controller design are analyzed and their performances are evaluated using IAE and ISE criteria. Centralized controllers are preferred when interaction is strong and decentralized controllers are preferred for weak interactions. Decoupling controllers eliminate interaction to a large extent and aid MIMO systems to be designed as many small SISO systems. The main work of the project is to design the decentralized decoupler for distillation process. PI controller is used to control the process. In order to design the PI controller are basically emphasized on the tuning parameters of the PI. To get the tuning parameters, various tuning methods are used such as Ziegler Nichols, relay sequential auto tuning method, BLT method, Optimal tuning (NDT) method are used in this process.