With the turn into the 21st century, people`s interest in Korean culture and Korean traditional costume(Han Bok) is getting highlighted and new term of ``Han Ryu`` has been begotten. (Han Ryu means big Korean cultural wave.) Han Bok as a component of Han Ryu is now on the move with the national interest and support. Analysis and modernization works on Han Bok especially traditional royal costume should be taken urgently when we consider its symbolic meaning, representativeness and diversity. To respond on this need, as a process of research, we explored and find the essential design elements of the aesthetic characteristics of Korean traditional royal costume, attempted to apply those elements to the costume of modern style by making it as following. As a result of our analysis of the characteristic of Korean traditional royal costume, it might be summarized as reverence-implying loftiness, stylish and pure dignity, and auspiciousness harmonized by yin and yang. We observed closely the elements of its` design such as pattern, color, and formation. In this paper design, motives were sought for out of traditional royal costume and hereby a few design works wearable in modern living were made. The work chose King`s formal dress that is relatively open for diverse modification in formation and color. Genderless characteristics of modern costume and suitableness of formal wear were also taken into consideration. Aesthetic characteristics of loftiness and dignity in King`s formal dress might be observed in its pattern. Most prominent pattern is dragon which has top position among mysterious animals. And auspiciousness in King`s formal dress can be observed in its color in compliance with the principle of yin and yang, and in its grand fold-on-fold formation. The work produced two suits of lady`s day time formal suit and an evening coat which are good in any occasion of official or cultural event. International designers including Asian adopt traditional elements and transfer them in the fast track of modernization. Especially, we are able to guess the trend of cross over using between the countries with similar culture and national background. Therefore, the effort to promote Korean excluded image and to produce competible goods should be continuous with protection of the essential traditional royal costume`s elements.