since the 1997 constitutional amendments stipulated the "semi-presidential" system in Taiwan, the new constitutional system has raised lost of discussions in both normative and operative dimensions. As time goes by, with the first regime turnover, more and more constitutional problems have emerged. Actually, there are many researches on Taiwan's constitutional system. Besides the approach of "old institutionalism", recently, the researchers also make use of the "new institutionalism" approach to argue how constitution changes in Taiwan. However, the old and new institutionalism are historically and methodobogically, derived from the same origin, while the concepts of "constitution" and "constitutionalismcan" can also relate to either of then. Therefore, from the comparative viewpoint of old and new institutionalism, this paper will analyze three main problems of Taiwan's constitutional operations revealed by the president-premier-Legislative Yuan interactions in theree dimensions, i.e., constitution, constitutional operation and the spirit of constitutionalism. The purpose of this paper is to establish a new analytical framework which and specify constitutional problems effectively, and suggest the solutions too.