Abstract: The Middle Ordovician Majiagou Formation is a set of marine carbonate rock strata. The formation is developed completely with stable distribution in Dongyao area of northern Henan Province, a favorable area to study the sequence stratigraphy. Based on the systematic study of surveyed profiles, with the rock assemblage and vertical variation rules of 8 lithologic members, two Type Ⅰ and five Type Ⅱ sequence boundaries are identified in the formation, which is further divided into 1 second-order sequence and 6 third-order sequences. The sequence stratigraphic framework of Majiagou Formation in Dongyao area is established by analyzing the characteristics of each order sequence. According to the features of sequence stratigraphy, it is believed that the sedimentary environment of Majiagou Formation in the area has undergone 6 transgressive and regressive cycles. The study can provide a reference for research of the Paleozoic sea level change in northern Henan Province.