Under the theoretical guidance of sedimentology, geophysics, and palaeontology, based on the analysis on cores, well logs, log data, palaeontologic traces, it is known that the sedimentary system of tidal flat were developed in the Silurian System Kepingtage Formation of Tazhong Area, Tarim Basin. The Kepingtage Formation includes grey-bitumen siltstone, greenish gray politic siltstone, gray medium-fine sandstone, gray medium-fine pebbled sand and developed feathering cross bedding, wave bedding, lensing bedding, thin sand and mudstone interaction layers, and low ration of sand to strata. Especially, the phenomena of the descending distribution from the central area to the margin of the basin and a great deal of feeding and dwelling trail of palaeontologic, all of these phenomena reflect an environment of tidal flat. The Kepingtage Formation is mainly in intertidal zone, subtidal zone, developing microfacies, such as subtidal sand jetty, sand-mud mixed flat of intertidal, and sand flat of lower tidal. Combined with analysis of laboratory data, the relationship between these microfacies and the distribution of oil has been discussed.