Summary: This paper proposes a design method of optimal tracking control for discrete-time systems with the delayed state and input. By introducing a new state vector, the original system is transformed into a non-delay discrete-time system with virtual disturbance. According to the optimal control theory, a sequence of discrete Riccati matrix equations and Stein matrix difference equations are constructed, and the solution sequence is proved to converge to the optimal tracking strategy of the transformed discrete-time system. By using the successive approximation design method of optimal control, the approximate solution of the optimal tracking control is obtained, and a design algorithm of the optimal tracking control law is presented. Simulation examples are given to illustrate the effectiveness of the proposed approach.