The development of Buddhist architectures of the Unified Silla period have been generally understood to have paired pagoda instead of one which had been popular until before the unification. Besides the stylistic categorization of paired pagoda system, there had been no further investigation reported concerning whether there was any detailed process of change within the development of paired pagoda style. This paper aims to identify such change inside the development of paired pagoda style, which, externally, seems to be the same pattern of site design maintained throughout the period of Unified Silla that lasted for about three centuries. Since the temple sites of study are in the same pattern of layout, the method of investigation has to be such that can identify the subtle changes that, in external appearance, are not easily discernible. Hence, this research compared the dimensions of important measurement of five temple sites to be able to clarify the process of minor changes. Among many sites of Silla temples, only five were suitable for the research since detailed measurement were possible through field research or the report of excavation. They are the sites of Sachonwang-sa, Mangduk-sa, site of Kunsuri, and Bulguk-sa. Although the five sites have the same style of paired pagoda, it is clear that there were consistant flow of change. Even though the motivation of such change were not strong enough to change the site pattern itself, it resulted continuous minor changes such as the size and location of architectures. The size of image hall, for example, was growing larger and larger as time goes on, while, the size of Pagoda was getting smaller. In the same way, the size of middle gate became smaller while the size of lecture hall became larger, although the rate of change in these cases were not as severe as that of image hall and pagoda. At the same time, pagoda was coming closer to the middle gate leaving larger space in front of the image hall. Such aspect is even more meaningful considering the fact that the pagoda, from the 8th century in Japan and China, moved outside of the major precinct. The image hall, too, moved toward the middle gate slightly so that the space in front of the lecture hall became more spacious. Such changes, of course, were not accidental but they are the same continuous motivation of change that caused the changes before the period of unification. Enlargement of image hall and reduction of pagoda, for example, represent the changing relative importance of religious meaning. Hence, it is evident that one can not easily imterprete the development of one style only by categorizing it to be one same style. In the veiwpoint of the underlying motivation of change, the fact that one style persisted for a certain period of time, does not mean there had been no change, but means that it was the time of motivational accumulation, causing minor changes within the same style, to be able to create major change coming after.