Abstract: A new method about parametric design of variational-wall-thickness blade body was provided, which could effectively solve the problem that how to modify the blade cross shape. It is convenient and effective to adjust the blade wall thickness, then to improve the blade performance. An effective method that how to acquire the mean curves was given and proved step by step, which could gain the real mean curves by using the geometric modeling function based on unigraphics (UG). It provides a technology route that realizes the parametric design of inner curves, and introduces a feasible plan to complete the work about parametric design of blade based on UG/OpenAPI; this route contains the thought of orient-object and the generative modeling style, and adopts undo-marks and the style of immediately recording the position of inner points. This developed module system can help users to dynamically modify the blade shape in real time.