Abstract: This study mainly focuses on the north of Songliao Basin with the purpose of investigating mudstone in the first and second member of Upper Cretaceous Qingshankou Formation. Through the collection and analysis of the data available in China and abroad, core description of topical wells and sample test data analysis, the authors studied the lithology, physical property, electric property, oil-gas possibility, hydrocarbon, brittleness and ground stress of mudstone in the first and second member of Qingshankou Formation. The results show that the first and second member of Upper Cretaceous Qingshankou Formation in the north of Songliao Basin has favorable petroleum geological conditions for the development of shale oil, and Gulong sag seems to be a favorable area of shale oil with good exploration prospects.