Since Taiwan has adopted semi-presidential system, there have been four directly elected presidents. But most of them needed to build decision-making mechanisms outside the constitutional system, trying to integrate government departments and the ruling party's views in order to form an effective government ruling team. After years of practices, it is clear that there is a challenge for our President to exercise his (or her) power to govern. That is, there is no viable constitutional organ of the President's formal policy decision authority. For this phenomenon, the existing semi-presidential research literatures rarely explored it. Based on the global perspective, this paper summarizes the experiences of 37 semi-presidential constitutional designs and further explores the arrangements for presidential policy decisions or consultation mechanisms under the constitution of the ROC, and analyzes the practical operation of the four presidents. Finally, this article reflects some challenges and suggestions for the constitutional design in Taiwan.