Just as culture is a collection of lifestyles, Cultural Properties is what is made over a long period of time and is left around us, whether it takes form or not. Many countries around the world have their own standards and are trying hard to preserve those with precious values. And in the case of Modern Architecture, because they are still in use In our daily lives and for the lack of recognition, they are continuously threatened during urban changes and developments. The purpose of the research is not to preserve Modern Architecture as done In the museum, but to seek a way for it to coexist with the changing environments of contemporary cities. Therefore, it is to recognize Modern Architecture as valuable assets, which expresses historicity in urban settings, and to seek the design characteristics of Modern Architecture. This is a process in order to find a new method for conservation of historicity. The result are as followings. Modern Architecture have their design characteristics and these can be applied as a design guideline. Therefore the form, material, and the colors of individual Modern Architecture can be analyzed so as to create a design guideline according to their styles. According to the analysis of Registered Cultural Properties in Seoul, they can be categorized into 6 uses and found the design characteristics of individual uses.