Since the late 20C, a lot of fashion designers have considered about new construction system in fashion. Many arguments about architectural form and construction system have being supported on enlargement of range of functionalism fashion through the consideration about new shape and combination among various any other spheres. Modular concept, which is able to divide complex construction of integration into separated basic unit and use various and liberal arrangements, is regarded alternative idea of economic construction that creates new shape and constructive beauty through the simple operation and changing combination continuously. Specially, fashion designs of Yoehlee Teng, John Ribber, and Galya Rosenfeld are estimated that they are effectively utilized architectural modular system pursuing multi-function and multi-change in fashion. Modular system utilized in fashion construction will be classified as follows: 1) layering system of Yoehlee Teng, 2) combine system of john Ribber, and 3) lego system of Galya Rosenfeld. This thesis will presents beneficial guide for simple and practical functionalism fashion design development in 21C.