The water cultural heritage of the capital functional core area is a historical witness of Beijing urban development and an important guarantee for Beijing to create an international first-class harmonious and livable city. By sorting out the water cultural heritage of the functional core area of the capital, constructing an index system for evaluating the value of water cultural heritage of the functional core area of the capital, proposing a grey correlation analysis method based on the combination of assignment and entropy weight, and combining with the evaluation index system to scientifically and objectively assess the value of the main water cultural heritage of the functional core area of the capital, in order to promote the management, protection and utilization of water cultural heritage units. It is found that the assessment results of the gray correlation analysis method based on the combination of assignment and entropy weights are highly accurate and stable compared with the traditional method. The value of the water cultural heritage of the Northem Moat, Jinshui River, Shichahai, Beihai and Taoranting is assessed to be Grade I, which has high socio-economic development value.