In this paper, an improved proportional-integral-derivative (Pm) controller optimized by extended nonminimal state space (ENMSS) model based model predictive control (MPC) is proposed for a typical multivariable process in the distillation column. The MPC optimized PM controller inherits the advantages of both methods, i.e., the simple structure of PID controller and good performance of MPC in dealing with industrial processes of coupling and time delay dynamics. In the ENMSS model constructed for MPC, the state variables and tracking error are combined and regulated separately, so that more freedom can be provided during the controller design and better performance can be acquired finally. A case study of a typical multivariable process in the distillation column under model/plant mismatches, disturbances, and measurement noises is introduced to demonstrate the effectiveness of the proposed method. In order to verify the improved performance of the proposed approach, a nonminimal state space model predictive control (NMSSMPC) optimization based PID controller is also considered as the comparison in the simulation.