Despite the differences in research targets and methods between sequence stratigraphy and petroleum system, the two theories are closely related in the analysis of oil- and gas-bearing basin. Because sedimentary rocks, the research object of sequence stratigraphy, is the container of oil and gas, and the research object of petroleum system, the analyses of sequence stratigraphy, includes analyses of necessary geological elements and pool-forming activities of the petroleum system, there is a close relationship between systems tracts, composition of sequence and necessary geological elements and pool-forming activities of petroleum system. Effective hydrocarbon source rocks are usually a condensed section of a sequence with a certain thickness and wide distribution, and overlaid strata of certain thickness in the geological history, and the condensed section is usually the maximum flooding surface of a tectonic supersequence. The main reservoir rocks are always located in the lows-standing systems tract of a sequence above the effective hydrocarbon source rocks or in the high-standing systems tract immediately above the effective hydrocarbon source rock. The blanket is usually the transgressive-standing systems tract and the condensed section of a sequence above the reservoir rock. The reservoir rocks of the lows-standing systems tract are usually terminated upslope, and therefore, lithologically trapped. Beside the fractures in strata, the incised valley sandbody of the low-standing systems tract of a sequence can be the migration passageways. It is usually that a petroleum system exists inter-sequencely, and sometimes even inter-supersequencely.