Abstract: Based on the GC,GC-MS and nonhydrocarbon nitric chemical compound analytical data of 21 samples of crude oil and hydrocarbon-bearing rocks,the geochemical characteristics of the Cretaceous oil in Wuerxun and Beier depressions in Hailaer Basin were studied,and the main source rock for the oil was determined by oil-source rock correlation.The studied results reveal that there are two kinds of crude oil in Wuerxun and Beier depressions.One kind shows a dominance of n-alkanes in C₁₇-C₂₃ and distribution in unimodality.Its Pr/Ph is higher than 1(1～2.88).The"V"shaped distribution of C₂₇-C₂₉ steranes and low gammacerane indicate a fresh water lacustrine source rock.The other one shows a dominance of n-alkanes in light hydrocarbons and low C₂₇ sterane.Its Pr/Ph is less than 1 and it lacks gammacerane.This kind of oil mostly stemmed from the coal measure strata.According to the results of oil-source rock correlation,the crude oils in Wuerxun and Beier depressions stemmed from two kinds of depositional setting.It indicates that there are good conditions of source rock in Hailaer Basin.