Abstract: The construction of an all-element monitoring and simulation platform of the water system based on space-ground integration is of great significance for improving China's comprehensive disaster prevention and mitigation,emergency management capabilities for floods and droughts,and ensuring national water security.On the basis of analyzing the needs of the water sector,this paper proposes a preliminary plan for the construction an all-element monitoring and simulation platform of the water system based on space-ground integration,consisting of a network (all-element observation network of the water system based on space-ground integration),a center (a big data center for water system science),and a platform (a smart simulation platform for water system).Among them,all-element observation network of the water system based on space-ground integrated will supplement the research and development of two X-band radar satellites and one P-band radar satellite to realize the full element,full cycle,all-weather and high-precision observation of the basin water system,aiming at the monitoring requirements of the full element of the water system.The big data center for water system science is based on big data,cloud computing,artificial intelligence,5G and other advanced technologies,in order to realize the storage and management of massive data of the water system in the basins,as well as the fusion of multi-source data and the inversion of water system elements.The smart simulation platform for water system will establish a supercomputing platform and the models for the whole water systems in the basins,with the support of the big data center for water system science,realizing intelligent simulation of different scenarios in the basins.All-element monitoring and simulation platform of the water system based on space-ground integration will comprehensively promote water conservancy remote sensing application and water conservancy informatization,and provide strong technological support for Chinese water security.