Abstract: This paper describes the concepts and features of BIM and parametric design. Aiming to solve the modeling difficulties due to the features of complex flow-through components in hydraulic machinery, the parametric design based on Dynamo for Revit is applied in the design of spiral case and draft tube, which realizes the "one-click modeling" of spiral case and draft tube. Compared with the conventional modeling method, the parametric design greatly improves the engineers' design efficiency, and fully reflects the application value of BIM in the design of hydraulic machinery.