Formation with dark mudstones of lake facies are developed of Funing Formation and the 2th member of Taizhou formation in Haibei Sub-sag. Through comprehensive evaluation for Cenozoic hydrocarbon source rocks by organic matter abundance, types and maturity and biomarker, it is considered that hydrocarbon source rocks of the 2th of Funing and Taizhou Formation have high abundance of organic matter and belong to better-good hydrocarbon source rocks, but hydrocarbon source rocks of 1th of Funing Formation are good-bad, hydrocarbon source rocks of 3th of Funing Formation are bad. The organic matter types of the 2th of Funing formation and Taizhou Formation are superior to that of the 1the and 2th of Funing formation. The organic matter type of the 2th of Funing formation is mainly of Ⅱ1-Ⅱ2, while the 2th of Taizhou Formation is mainly of Ⅱ2. The organic matter of hydrocarbon source rocks has a low degree of thermal evolution, but some samples of hydrocarbon source rocks are at maturity stage. The hydrocarbon source rocks of the 2th of Funing and Taizhou Formation occurred in the semi-deep – deep lake with reduction and high salinity, and the organic source material is mainly brackish-water algae and higher plants.