This study attempted to comprehend the usage of the modular system in fields through literature review and objective research, as well as analysis of its expression characteristics in fashion. It tried to provide inspiring visual data for the fashion design of the modular system. After analyzing architecture and product-related books, Internet data and advanced research, the four expression characteristics of the modular system were obtained. Firstly, the formative expression characteristics of the modular system in fashion were simplicity, extensibility, variability and diversity. Secondly, of the formative expression characteristics expressed in modern fashion, simplicity (30%) was the highest, followed by extensibility (27%), diversity (22%) and variability (21%). Thirdly, simple silhouette and structure were used to express simplicity, usually simple geometric figures. In contrast, extensibility was expressed through the expansion and exaggeration of the area, length and volume of the clothes. In terms of variability, the typical characteristics of modules were reflected. For diversity, heterogeneous materials were used, and informality was expressed.