Abstract: On the basis of geochemical characteristics of oil samples collected from Xinglongtai structural belt in the west Sag of Liaohe Depression crude oils found in Xinglongtai structural belt were classified into four types.Carbon number distribution curves of normal paraffin hydrocarbons mature parameters of steranes and terpanes, and Pr-to-Ph ratio varied alet and distributied regularly.The maturities and Pr-to-Ph ratio of the Tertiary oils in the structural belt show an decreasing trend from south to north and proportionally the carbon number distribution curves of normal paraffin hydrocarbons change from unimodal distribution model to bimodal distribution model The curde oils from the reservoirs of the inner and surface layer of the buried-hill have similar geochemical characteristics and higher maturity than the Tertiary oils.The relationship between thermal evolution difference of source rocks in peripheral hydrocarbon generation subsags and develpment of faults is mainly responsible for the distribution of crude oil