Abstract: According to an ancient document Bamboo Annals, the day dawned twice ("double dawn") in Zheng (郑) during the first year of King Yi of Zhou (周懿王), and it has been regarded as a solar eclipse happening around sunrise by modern scholars. The annular eclipse on April 21th, 899BC is chosen as the candidate of "double dawn" eclipse by the Xia-Shang-Zhou Chronology Project. Besides, the more general researches confirm that only eclipses with magnitude more than 0.95 can cause the phenomenon "double dawn", and the altitudes of sun during eclipse are constrained as well. After defining "Zheng" in Fengxiang county, Shaanxi, we use astronomical software to imitate the solar brightness change during the 899BC eclipse and the 1997 eclipse, which was observed by the Chronology project. As a result, we confirm that the "double dawn" is a general phenomenon, derive the specific process and some particulars of the "double dawn" eclipses.