Abstract: The current flood forecast in the Changjiang River Basin is carried out based on the idea of deterministic forecasting, in which the risk information provided to decision makers is limited, so it is urgent to develop probabilistic forecasting technology.At present, most probabilistic forecast in China is still in the research stage, which means that there is no perfect and practical operational method to follow.On the basis of summarizing the current status of flood forecasting in the Changjiang River and the research of probabilistic forecast at home and abroad, we propose a complete set of technical systems for flood probabilistic forecasting in terms of basic principle, the construction of model method library, business process and product form, which can be used for flood probabilistic forecasting in the Changjiang River Basin.