Hao Datong's Dan-dao theory incorporates Yixue and Zhouyi Cantongqi. It is not only compatible with Laozi's interpretation of nature but also based on the essence of Yixue way of thinking-observation of nature, and on the flux of yin and yang. Most of the Yi-diagrams Hao has developed are reflections of traditional cosmology, an important feature in his Dan-dao theory. The present study is a two-part study with the aims to analyze Hao's cosmology from his more than twenty Yi-diagrams found in his Taiguji. Besides, from scarce literature, a diagram of the universe, time, and space based on his outlook on nature is reconstructed by interpreting his most representative Yi-diagrams. The importance of yin and yang is manifested throughout all of Hao's diagrams. His diagrams of the numbers of heaven and earth, qian and kun, sun and moon, He-luo, and Wuxing are all designed according to the natural flux of yin and yang, and he proposes that time and space in the universe are both anchored by yin and yang. The first part of the study explores Hao's view on Tiandao, with the focus on Dao-qi and his framework of the flux of yin and yang, interprets his cosmology from qian and kun, and explains the significance of the time and space dimensions of Yi-gua derived from qian-kun.