Abstract: Oil-oil meticulous correlation research shows that there exist both immature and mature oils in Oulituozi area of the Liaohe Basin,and the maturity level of these oils is generally lower than those in the other areas of the East Sag.The lower maturity level of the oils in Oulituozi area is reveald by the following aspects:the ratio of saturated to aromatic hydrocarbons is low(3.0),the values of the maturity parameters of biomarkers and the stable carbon isotope values of saturated hydrocarbons and aromatics(-26.00‰～-27.50‰ and -25.00‰～-26.50‰ respectively) are also lower respectively than those in the other areas of the East Sag.The characteristics of the isotope contours of various individual hydrocarbons also indicates that the maturity of the oil in Oulituozi area is low.The results of oil-source correlation research suggest that the crude oil in Oulituozi area comes from the dark mudstone layers of the middle and lower parts of the 3rd member of Shahejie Formation,and the results of biomarker research show that the thermal evolution degree of the source rocks in Oulituozi area is apparently lower than those in the other areas of the East Sag,which causes the low maturity of the crude oil in the area.