Aiming at the communication burden associated with traditional methods for voltage control in distribution networks, this paper proposes a model-free adaptive cooperative voltage control. This strategy is built upon an adaptive threshold-based event-triggered mechanism. The proposed method operates effectively without relying on a mathematical model of the system. Its core innovation lies in the design of an intelligent event-triggered mechanism that integrates a dynamic triggering threshold with an adaptive dead zone. This integrated design is key to achieving a substantial reduction in the controller's communication frequency and computational load. Simulation results comprehensively verify that the proposed strategy successfully maintains high-precision voltage control while simultaneously achieving a significant reduction in the triggering frequency. Consequently, this approach provides a practical and efficient solution for addressing the challenges of cooperative voltage control in modern distribution networks, particularly those with constrained communication resources.