Abstract: The content of C and H in the high pour-point oil of Shen84-An12 Block in Liaohe Oilfield was measured by element analyzer, and then the major components of this oil were analyzed. The oil's carbon number distribution was obtained by GC. Combining with element analysis and the carbon number distribution, the relative molecular mass of the oil was calculated. The results show that saturated alkane is the major component of this oil because that the contents of C and H reached the sum of 99.21%, and the ratio of hydrogen atom to carbon atom is 2.10; the distribution of carbon number of crude oil is from nC₁₂ to nC₃₅, and the good analysis results about the distribution of the carbon numbers in the oil have been obtained by the chromatography conditions described in the paper; the molecular mass of the high pour-point oil of Shen84-An12 Block in Liaohe Oilfield is 334.98, which was calculated by the content of carbon and the distribution of the carbon numbers. In addition, calculating value is 332.92 by the content of hydrogen and the distribution of the carbon numbers. The difference value is 2.06.