Abstract: In Erlian basin,Neopaleozoic marine-paralic clastic and carbonate sedimentary formation developed well. The host formation has no regional metamorphism. The dark mudstone and carbonate source rock well developed. Based on the geological research and the primary analysis and evaluation of source rock, six source formations(Niqiuhe, Benbatu, Amushan,Shoushangou, Zhesi, Linxi) and several profitable source-reservoir-caprock assemblages are determined. The source rock standard of the dark mudstone(limestone) is moderate-good. The organic material is classified in Ⅱ2-Ⅲ type. Thermal evolution degree is mature-condensate oil and humidity. The dark mudstone(limestone) is in high potential of hydrocarbon and can be taken as the new crucial exploration formation in Erlian basin.