Beijing City Master Plan(2016 – 2035) requires protecting the traditional central axis and its traditional features by strengthening the comprehensive improvement, combined with the application for the World Heritage List, of key areas, such as Bell Tower and Drum Tower, Yuhe River, Jingshan, and Tianqiao. To achieve these aims, the primary questions that have to be addressed are where the central axis of Dadu of the Yuan Dynasty was and what relationship it had with that of the palace of the Yuan Dynasty, as well as that of Beijing in the Ming and Qing Dynasties.It is noted that the planners of Dadu set the central terrace as a basic control point for planning and design, which was at the central point and on the central axis of the capital city. Therefore, the central axis of the capital can be probed into by figuring out the position of the central terrace. This paper first of all finds that the central terrace was located to the east of today’s Drum Tower(named Qizheng Tower in the Yuan Dynasty) based on relevant literature. Then using the method of Collineation Measurement, the paper restores the process of Liu Bingzhong determining the central terrace based on the geographical condition, and delimits the possible area where the central terrace was located in. Furthermore, combined with site exploration and ancient maps, it basically identifies the exact position of the central terrace and finally confirms the direction of the central axis of Dadu in the Yuan Dynasty, revealing the fact that the central axis of Dadu coincides neither with that of the Forbidden City in the Yuan Dynasty nor with that of Beijing in the Ming and Qing Dynasties. In brief, this research provides a reliable historical basis for actively promoting the central axis applying for the World Heritage List, protecting the traditional central axis, and strengthening the overall conservation of the old city.