Abstract: Based on the sequential stratigraphic research, this paper is focused on the environment for hydrocarbon source rock of the Paleogene System in the sequential stratigraphic framework of Qikou Depression by means of organic geochemistry, studying the distribution law and controlling factors of high-quality source rock. The Paleogene System in Qikou Depression can be divided into three secondary sequences. A number of sets of effective source rock developed in the strata of different sequences, but source rock is strongly heterogeneous. The different sequences are divided into six types of sedimentary organic facies according to the differences in the palaeoenvironment, palaeoecology and palaeoclimate. Of those types, the high-quality source rock of near source - saline lake - strong reduction atmosphere - plant and algal source facies developed most. Vertically, high-quality source rock developed mainly in the faulted lacustrine basin in the stable lake flooding period, particularly in the upper part of SQEs₃ 2 - SQEs₃ 1, the upper part of SQEs₁ lower - SQEs₁ middle. Horizontally, high-quality source rock development mainly in the southern part of Qikou Depression because it was controlled by the conditions of material sources and the environment of water bodies. The sedimentary and sourcing environments controlled space development of highquality source rock in common.