As the first batch of pilot projects of digital twin water conservancy construction of Ministry of Water Resources,the development of its knowledge base is the core component of digital twin Xiaolangdi,which is technically difficult,and the application of business scenarios is facing great challenges. This paper carries out systematic research on the development of digital twin Xiaolangdi knowledge base,which adopts the knowledge base architecture system composed of knowledge engine,knowledge base,and knowledge application. Meanwhile,this paper realizes diversifi ed services such as retrieval,question and answer,recommendation and reasoning decisionmaking based on water conservancy knowledge,and carries out practice and verifi cation in the “four pre” business applications of digital twin,which provides significant support for the core business of Xiaolangdi hub such as engineering safety and fl ood control scheduling. The construction of digital twin Xiaolangdi knowledge base in this paper thus provides signifi cant reference value and practical signifi cance for similar water conservancy projects.