Abstract: The Ordovician system in Yichang district is divided into three II type sequences by using the principle and method of outcrop sequence strtigraphy. The characteristics and their sedimentary dynamic mechanism of the individual system tractst, the controls of sea level changes on sedimentary process, organism migration and the environment are elucidated as well. It is believed that there are three sea level change cycles during the Ordovician period in the study area: the first one occurred from early to late Lianghekou age; the second one from the end of Lianghekou to the beginning og Dawan age; and the third one from early Dawan age to terminal Wufeng age. Two keep-up type carbonate systems are recognized. The result shows that the Lower Ordovician bioreefs in Yichang district formed during high sea level periods. The early Wufeng age reached the maximum of sea level rising, and the Wufeng shale is considered to be a typical condensed section, while the Guanyingqiao Member formed within high sea level period. Based on the analysis of the sedimentary rate, ecologic and sedimentary aspects, it is believed that both the Wufeng shale Member and the Guanyingqiao Member are formed in deep sea basin environment.