Abstract: This paper discusses the optimal tracking control of linear discrete time-delay systems. The system with control-time-delay and direct path between input and output variables is discussed first, and then a general form of time-delay systems is analysed. An extended state vector involed all the time-delay variables of the original system is constructed to get an extended new system without time-delay. Using the optimal feedback control theory of LQI, this paper gives optimal control tracking algorithm and the conditions of stability and exact tracking of close-loop systems. Finally, a simulation study on an industrial electric heater is carried out. The result shows that, in the situation of temperature setpoint changes, the optimal tracking control can result in fast exact tracking with small deviation.