Plug-Flow Reactors (PFR) belong to frequently used technological plants which exhibit unpleasant behavior. The traditional PID control structure in these cases may fail or demonstrate an unacceptable behavior. The paper brings another approach of control design called robust. It means that the controller is fixed but resistant to the uncertainty of the controlled plant. The studied approach considers a linear system with parametric uncertainty, which covers a family of all feasible plants. A controller with fix parameters is then designed so that for all possible plants, the acceptable stable control behavior is obtained. The structure of the control law is in two degree of freedom (2DOF) which offers better control responses than classical structures. All calculations and simulations of mathematical models and control responses were performed in the Matlab and Simulink environment.