Abstract: Lower Cretaceous Jiufotang Formation is one of the important source rock stratigraphic horizon in Mesozoic strata of western Liaoning Province. It is widespread in Jianchang-Kazuo Basin, with thickness of 206~2118m, but is relatively thinner in Fuxin-Yixian Basin. Organic geochemistry analyses indicate the two basins have both developed good to excellent source rocks characterized by good kerogen type and low maturity. The second section of Jiufotang Formation, which was formed in flunctuating profundal facies, is optimistic source rock horizon with average TOC of 9.5% and kerogen ofⅠtype. The first and third sections of Jiufotang Formation, which were formed in fluvial-lacustrine facies, have relatively poor source rock development environment due to shallower water body. The biomarkers analyses indicate that source rocks in the second section of Jiufotang Formation were developed in a clay-rich reducing brackish lake. The preliminary genetic analysis indicates that the development of these source rocks was attributed to good conservation condition from chemical stratification of lake water body and relatively high primary production.