直接建模為目前市面上多數CAD (Computer-Aided Design)軟體所使用的建模方法，但多數CAD軟體在修改功能上並未與特徵辨識進行結合，其目的主要為模型編輯之靈活性。然而，當使用者欲修改模型中多處之幾何外形時，則須手動選取，此過程較為浪費時間，因此本研究擬在Rhinoceros平台發展出一套針對模型中之肋特徵設計變更之系統，並依據肋特徵須修改之種類發展出五項修改功能。本研究以模型的B-rep資料結構與肋特徵辨識之結果為基礎建立特徵中點、邊、面彼此拓撲關係，並以曲面移動、旋轉與計算幾何之方式推算變更後之形狀來改變其幾何資訊，以達到變更之目的，對於變更後之結果，本研究以原模型與變更後模型之體積差，作為是否完成變更修改之依據。;Most CAD software in the market use the technique called direct modeling to build up models. However, most CAD software do not combine with features recognition in modifying. Doing the features recognition can make the modifying easier. When users need to change designs in many features, users need to choose the features by hand. This process causes lots of time. Therefore, our study develops a system to modify ribs in thin shell parts on Rhinoceros platform. And according to different types of ribs, our study develops five functions to modify. Our study uses the B-rep data structure and the results of rib feature recognition to build up the topology relationship between points, edges and faces. Using these information to translate surfaces or rotate surfaces after calculating the expected results. Moreover, changing the geometric information in order to achieve the design changes. For the modifying results, our study checks the difference of volume to be our rest on modifying successful or not.