Abstract: Molar-tooth(MT )limestone is a special type of limestone developed in the Meso-and Neo-proterozoic carbonate platform.MT limestone is very well developed in the middle part of the Sinian Yingchengzi Formation in the Dalian area in the southern Liaodong Peninsula.Based on the field observa-tions and thin section examination,as well as the comparative sedimentologic study,the appearance of MT limestone is closely related to the diagenetic environment ,and its location is related to the sea-flood-ing events.According to the study of the meter-scale cycle,in this rock facies segment ,mainly meter-scale cyclothems of shallow-water carbonates rocks are developed,and MT structure dominantly occurs in the moderately thick-to thin-bedded micrite and calcisiltite in the middle and lower parts of this micro-cycle,which indicates a subtidal shallow-water environment.