AbstractA set of lacustrine limestones，several to tens of meters thick，are the main deposits in the lower part of Member 3 of the Nadu Formation in the Tiandong Depression of the Baise BasinThe rocks range from light grey to grey in color，with abundant gastropoda shell fossils and oncolites，and are interbedded with thin mudstones and calcareous argillaceous siltstonesIn this paper, the petrologic characteristics of the lacustrine limestones are studied in detail on the basis of core observation and outcropAccording to a large number of features of the primary sedimentary structures，fossils，sedimentary geochemistry and welllogging facies，the sedimentary facies of lacustrine limestones are divided into three subfacies，ie，coastal lake，grain bank and shallow lakeThen eight microfacies are recognized，including the calcareous mudstone tidal flat，swamp，grain flat，bank edge，bank ridge，interbank channel，limemud shallow lake and argillaceous shallow lake，and the sedimentary characteristics of each microfacies are also studied in detailIt is concluded that the lacustrine limestone was mainly deposited in the grain bank located in the shallow lake and the sedimentary facies model is proposed through mapping the regional distribution of lacustrine limestone and the layout pattern of sedimentary facies