It deals with event-triggered reduced-order H ∞ filter synthesis of discrete-time uncertain switched systems. It is considered norm-bounded uncertainties affecting the uncertain switched systems’ behavior. An event-triggered strategy is firstly specified to identify whether information of the uncertain switched system is transmitted or not. Then, a reduced-order H ∞ filter is designed ground on outputs of the proposed event-triggered strategy. And utilizing the merging switching signal technique, a switched filtering error system is modeled by the uncertain switched system and reduced-order H ∞ filter. Subsequently, some sufficient critera are presented to guarantee that the switched filtering error system is exponentially stable with a weighted H ∞ performance. A design method is also given for the reduced-order H ∞ filter. Finally, the validity and feasibility of this study is illustrated by a practical example.