Abstract: The section of top Majiagou Formation is located in the east of Niumaoling Scenic Area of Benxi National Geopark. The sedimentary environment of the section is restored and its change rules are summarized through the microfacies analysis of carbonate rocks. According to the study of specimens, 14 microfacies types are classified, including 1 tempestite microfacies type, 9 gentle slope microfacies types, 3 standard microfacies types and 1 custom microfacies type. The section can be divided into 3 low-energy upward-shallowing tidal margin cycles from bottom to top: The sedimentary environment of Cycle I is tidal margin or lagoon of inner gentle slope-sandbeach and sand bank-tidal margin of tide gate; The sedimentary environment of Cycle II is from limited or open inner gentle slope to shallow subtidal zone of tidal margin and intertidal-supratidal zone of individual layer; The Cycle III is the most typical, with the sedimentary environment from the middle gentle slope of gray limestone, to tidal margin, then to the tidal margin shallow subtidal zone of yellow carbonate rocks, to the evaporative lagoons of intertidal-supratidal zones, and to the evaporative coast of intertidal-supratidal zones in arid climate. It is inferred that the stained Fe³⁺ and clay minerals are of terrigenous origin, and the section point is the tidal margin environment of carbonate rock island (bar).