Abstract: The key structure during Early-Middle Jurassic in Mongolia is subduction and closure of the Mongolia-Okhotsk ocean. To the north of the ocean there develops a group of back-arc extensional basins, whereas to the south of the ocean there exists an amalgamation continent, where the fossil geosutures are rejuvenated by the subduction orogeny and inland orogeny occurs. In Inner Mongolia of China, there develop three molasse basins related to the inland orogeny, all of these basins stretch into Mongolia, so that the molasse basins in eastern Mongolia have the same geometric and kinematic features as that in Inner Mongolia. The typical stratigraphic columns in the above-mentioned four basins are briefly illustrated. Although there are distinct lithologic and coaly characters constrained by the same orogeny, the sedimentary records show some similarities in all of the basins, such as thick conglomerates in the basal part, a upward-fining succession, and the coal seams in the middle part of the column, etc. Based on the similarities, the evolution of Early-Middle Jurassic basins can be divided into three stages, namely, the pre-coal-forming stage, coal-forming stage and post coal-forming stage. The creation of economic coal fields are controlled by the structure (depositing space) and climate (supplies of mother substance of coal) in the coal-forming stage.