This paper is devoted to solving the problem of sliding mode control for discrete-time switched systems with disturbances via an improved event-triggered strategy. First, the switched sliding mode dynamics is obtained based on the pre-designed sliding mode surface. Then, on the basis of the Lyapunov functional technique and the average dwell time approach, sufficient conditions for the existence of the concerned sliding mode dynamics are established. Third, the sliding mode control law is synthesized such that state trajectories of the considered switched system can be driven into the bounded sliding mode region and maintain there subsequently. Moreover, the event-triggered scheme is proposed in close combination with key feature of sliding mode control, which is different from the most existing works. Finally, two examples including a single-link robot arm system are given to show the effectiveness of the proposed design method.