This article focuses on the issue of non‐fragile control for a networked control systems (NCSs) with randomly occurring nonlinearities, where an advanced dynamic event‐triggered mechanism (DETM) is introduced. First, an improved DETM transmission strategy for NCSs is proposed. Based on the dynamic error of the system, the improved DETM can adaptively adjust the threshold to control the transmission of signals. The balance of the network bandwidth and control performance is excellently regulated by the adaptive threshold rather than a predetermined constant. Second, by taking the networked‐induced delay, DETM, randomly occurring nonlinearities and controller gain perturbation into consideration, a nonlinear system model is established. Next, sufficient stability conditions that can guarantee the mean‐square asymptotical stability are obtained based on the novel two‐side Lyapunov‐Krasovskii functional (LKF) and second‐order generalized free‐matrix‐based integral inequality (GFMBII), which contains more system information and can provide less conservative results. Finally, two numerical examples are presented to verify the advantages of the proposed method.