Abstract: The energy-intensive character and operating flexibility of seawater desalination plants(SDPs) make them ideal resources for demand response. However, the existing studies on the coordinated operation of SDPs and the power grid mostly concern integrated scheduling while lacking adaptability to autonomous decision-making scenarios. Moreover, the operational constraints of SDPs are roughly presented. In this paper, a coordinated operation method between reverse osmosis SDPs and a regional water-energy nexus (WEN) is investigated. Considering the production process, regulation characteristics, and operational constraints of SDPs, the water-energy management models of conventional SDPs and renewable energy-powered SDPs are established, respectively. Furthermore, respecting autonomous decision-making and information privacy between the two types of SDPs and the regional WEN, two coordination mechanisms based on the interaction of the scheduling plans, namely, the "incentive-based" and "price-based" coordination mechanisms with their scheduling models are proposed, and a method based on second-order cone relaxation(SOC) and McCormick envelope is also proposed. The effectiveness of the proposed coordination mechanisms, scheduling models, and the method are verified by case studies.