An event-triggering mechanism with variable threshold for model-based event-triggered state-feedback control system is propoesd. When strong and fast varying disturbances act on the plant, this event-triggering mechanism can enlarge the threshold automatically to mitigate the unnecessary waste of communication resources. When slowly varying disturbances act on the plant, this event-triggering mechanism can avoid the communication network lies idle by using a timetriggering mechanism. Meanwhile, this event-triggering mechanism can also decrease the threshold automatically to improve the control performance. Simulation results show that, compared with the fixed threshold event-triggering mechanism, the proposed variable threshold event-triggering mechanism consumes less communication resources, but makes better whole performance.