Abstract: High dip-angle(>10°) oil area in the Block Qi 40, located in the middle-southern part of the western slope in the Western sag of Liaohe rifted basin accounts for a large proportion of the steam flooding pilot areas. The high dip-angle oil area has entered the late development stage, which is characterized by continuous decline of oil production and rising production cost, so that to explore effective successive development method at the late steam drive stage for inclined reservoirs and to further enhance oil recovery have theoretical and practical significance. 4 typical well groups are selected in the high-dip angle area of western Qi 40 block, and 3D geological model and numerical model are established by using Petrel and STARS softwares, respectively, then study on optimization of successive development methods at the late steam flooding stage is carried out. Numerical simulation result shows that the producing degree of Lian I oil member is relatively high; that of Lian II oil member is relatively low with the residual oil saturation higher than 60%, and small differences exist in residual oil distributions at the high and low positions of the structure. According to the characteristics of residual oil distributions in Lian I and Lian II oil members, it is considered that separate layer steam injection technology can be used and the oil recovery factor by the technology can increase by 4.0%. The optimization result of the successive development methods at the late steam flooding stage for the inclined reservoirs in the Block Qi 40 shows that the oil recovery improved by intermittent steam flooding is the highest, reaching 5.2%; that improved by continuous steam flooding is 4.6%; those improved by alternate steam-water flooding and steam-air combination flooding are 1.8% and 3.2%, respectively. The producing degree by intermittent steam flooding is larger than those by continuous steam flooding in LianⅠoil member; the cumulative oil-steam ratio by intermittent steam flooding is higher than those by steam-air combination flooding and alternate steam-water flooding. Therefore, it is suggested that intermittent steam flooding should be the optimal successive development method at the late steam flooding stage.