In order to explore its application benefits, an evaluation index system for the application benefit of BIM in hydraulic engineering is established from the perspectives of economy, resources and energy, technology and management on the basis of literature reading. Firstly, using the SEM idea, a questionnaire survey is used to conduct the confirmatory factor analysis of the evaluation system, and thus the index weights are obtained accordingly. Secondly, an evaluation model for the application benefits of BIM in hydraulic engineering is established by using the cloud matter-element theory. Finally, a case study of a water conservancy project in Guangxi Province is carried out. The results show that the level of application benefits of BIM is Grade 3 with good benefits. Accordingly, the relevant suggestions are put forward to promote the further development of BIM in hydraulic engineering.