Study of lithologic character, sedimentary structure, paleontology and geochemistry as well as sedimentary facies, sedimentary circulation and sedimentary model indicates that the coal-bearing formation in the Songba ore block, Junlian coal mine was formed in tidal flat-lagoon depositional system and consists of lacustrine facies, lagoon facies, tidal flat facies and peat moor facies. Major mineable seams were formed in back barrier peat moor facies. Change in thickness and quality of coal beds is controlled by topography, water level and marine roof.