Abstract: The Caohu Sag is located in the North Manjiaer Depression of the Tarim Basin. Its source rocks are the Cambrian and Ordovician melalimestone of the Lower Paleozoic, and its reservoir rocks are the Ordovician limestone and Carboniferous Donghe sandstone of the Paleozoic as well as the Triassic, Jurassic and Cretaceous sandstone of the Mesozoic. The sag, petroleum geologists be of the same view, is a very prospecting region for hydrocarbon exploration. Based on the theory of petroliferous systems, thedeep O₂₊₃-C₁ petroliferous system and the upper T-E₁ composite petroliferous system are divided, and the matching relationship between the hydrocarbon generation and expulsion of source rocks and the developing periods of traps as well as the patterns and pathways of hydrocarbon migration is discussed. Furthermore, the understanding of hydrocarbon enrichment regularities for the sag is strengthened, and the direction and targets of hydrocarbon exploration in the sag are suggested.