Abstract: Erlian Basin is a Mesozoic continentians basin developed on the Hersian folding basement.Lower Cretaceous Aershan and Tenggeer Groups and Jurassic formations are the main deposits.Sags in the basin and distributed en lunchen showing the characteristics of action of tensional and torsional force during their formation.Affected by factors such as the structural lines of the basement,boundary conditions and the nonuniformity of the action of the geological forces,the depth of depressions as well as their sizes differ greatly,and show a feature of sectioning and belting distri-bution.Strong tensional and torsional depressions are formed mainly along overlapped areas of NNE-NE and nearly E-W of the basement structural lines,the former depressions being large and deep usually,and the later ones being narrow and shallow.The size of tensional depressions developed on the base of NE-NNE basement sructural lines in the nothern part are greater than those deve-loped on the E-w structural lines in the southern part.As a result of exploratory drilling,5 types of oil reservoirs are discovered.All of them are located in the tensional depression zone.The oil in them being origin-ated from lower cretaceous accounts for 80% of the predicted resources.All the oil and gas are find on the area surrounding the oil-generation sags.However,strong reforming action due to later tectonic movement were occured.Jurassic oil and reservoirs and coaliferous gas reservoirs may be found as more exploration is carried.