China's water conservancy and hydropower enterprises continue to face the challenge of lagging hydropower standards despite being a major player in the construction of water conservancy and hydropower projects. This paper presents a theory for evaluating the social integration process of immigrants in water conservancy and hydropower projects. The theory aims to promote China’s ‘Belt and Road’ strategy, enhance China’s modernization, and establish China’s right to speak. The paper explains the overall framework, process evaluation, and result evaluation of the theory. The evaluation process can be divided into three periods: planning, placement, and later support. The result evaluation is divided into three aspects: environmental adaptation, population development, and cultural integration. Using the Three Gorges Project as an example, this text preliminarily tests the science, rationality, and feasibility of the entire assessment theory. In the future, research on engineering immigration should expand the application scope of the whole process assessment. Sufficient attention should be paid to the problem of social restructuring, and efforts should be made to build an assessment system with Chinese characteristics.