Based on the drilling, well logging and seismic data, through introduci conversion surface and applying the theory and method of high-resolution sequence grade datum level cycles as the referring interfaces, the sequence stratigraphic studi ng the concept of depositional stratigraphy taking the multi- es on the Qingshankou Forma- tion-Yaojia Formation in the front belts of West Slope of South Songliao Basin are conducted. Four long-term base level cycles and eight medium-term base level cycles are recognized altogether, and then the sequence classifying programs are established, on the basis of the sequence stratigraphic contrast of the well-commingled profiles, the stratigraphic framework is built; the studies show that Qingshankou-Formation bottom/lower sequence deposits in the period of fast water-transgression and the upper sequence of Qingshankou Formation belongs to the period of the water-regression, and moreover the upward Yaojia-Formation sequence is located in the initial stage of another wa- ter-transgression ; besides the stacked patterns of each cycle change regularly with the rise and fall of the level, the distribution types of sequence framework also possess remarkably influences on the oil and gas migration and accumulation.