This paper investigates an H_∞ static output feedback for a low-frequency (LF) networked control system (NCS). A decentralized event-triggered scheme (DETS) is proposed to reduce the network communication loads. The LF NCS with the DETS is modeled as a time-delay system with an LF constraint. With this model, H_∞ performance analysis is developed via an LF integral quadratic constraint method and a generalized Kalman-Yakubovich-Popov lemma. Furthermore, a detailed controller design algorithm is presented to obtain an H_∞ static output feedback controller for the LF NCS with the DETS via a two-stage approach. The numerical results are provided to demonstrate the effectiveness and superiority of the proposed techniques.