Abstract: In basins with severe natural water resource depletion, ecological replenishment of river-lake systems has become one of the important ways to restore lake water ecosystems. In order to improve the scientific nature of ecological water replenishment in the river-lake system, this study took Baiyangdian Lake as an example to design and develop a decision support system of integrated monitoring and simulation model for ecological water replenishment quality of the upstream river of Baiyangdian Lake. The system covers the core functions of basic geographic information query, real-time dynamic monitoring of surface and underground water quantity and quality, coupled simulation of water quantity and quality of upstream river recharge channels, prediction of water level in Baiyangdian based on the water balance model, and comprehensive control scheme library of ecological water supply and water pollution prevention. This system can provide decision support for the scientific and efficient formulation of a comprehensive guarantee plan for the ecological replenishment water quantity and quality of Baiyangdian Lake under the joint influence of climate change and human activities, and provide reference for the development of decision support platforms in the field of environment and water conservancy based on big data and cloud computing.