Against the backdrop of China’s modern social transformation, the cheongsam emerged from the form of Qing Dynasty banner clothing, achieving an essential leap from a “carrier of feudal etiquette” to a “modern cultural symbol.” Its aesthetic evolution was not merely an iteration of clothing styles, but a cultural phenomenon deeply intertwined with institutional changes, ideological emancipation, and technological innovation—from the broad, heavy traditional form to modern tailoring that fits the body’s curves, and from a status symbol of hierarchical order to a fashion medium for women’s self-expression. Each aesthetic adjustment of the cheongsam bears the marks of the times. Based on documentary research and an interdisciplinary perspective, this paper traces the historical inertia of the feudal clothing etiquette system, analyzes the core driving force of institutional relaxation in the late Qing Dynasty and early Republican period, and reveals the social and cultural logic behind the cheongsam’s evolution. It provides a unique costume history perspective for understanding changes in gender relations, cultural psychology, and social structure in modern China.