Cheongsam has already become Chinese national apparel beyond world philosophy. The name "cheongsam" is not a name that is born with. Over the past 100 years, it underwent three periodical changes, namely under-robe → cheongsam (improved cheongsam) → kei robe. The evolution from "cheongsam" to "kei robe'" is a landmark in China's modern costume history, because it overturned the traditional "cross planar construction." However, the academic world has not conduct a systematic summary of the situation. Scholars in Mainland China and Taiwan have not yet achieved an agreement. Based on the review of historical facts, literatures and academic study in Taiwan, this paper explores the process and three forms of the change from "Under-robe" to "kei robe," which is of vital significance to the periodical costume historical study from the late Qing Dynasty to the Republic of China and to the establishment of a new China.