Abstract: At present, traditional water conservancy is rapidly entering a new stage of high-quality development for intelligent water conservancy.It is an important component of building a digital twin watershed to develop an intelligent watershed hydrological simulation and flood forecasting system.It is also an inevitable requirement for strengthening the "four precautions"(forecasting, alarming, preview and plan) and promoting the construction of intelligent water conservancy.The research progress of hydrological simulation forecasting is reviewed, and the current situation and shortcomings of the application of flood forecasting systems in China are analyzed.Meanwhile, we discuss the key technologies and development prospect of intelligent basin hydrological simulation and flood forecasting system from the aspects of database, regular mechanism, forecast model, methodology and technology, and application platform, including: pooling multi-source heterogeneous data and consolidating basin database; strengthening the water vapor cycle study of river reservoir system and revealing the cause mechanism; focusing on characteristics of strong human activities and upgrading professional models; deepening the research of new forecasting technology and exploring the integrated business system based on intelligent forecasting and dispatching; building a general business platform to support the multi-factor full cycle "four precautions" function.The research results can provide a theoretical basis and technical support for improving the flood forecasting level in river basins, strengthening the "four precautions",and constructing digital dual river basin.