Abstract: The asphaltene of a biodegraded oil from Caoqiao oilfield,Dongying depression,Bohaiwan Basin has been investigated by ruthenium-ions-catalyzed oxidation technique (RICO).The products of asphaltene RICO included n-alkanoic acids,dialkanoic acids,tricyclic terpernoid acids,hopanoic acids,gammacerane carboxylic acids,pregnanoic acids,sterane carboxylic acids and so on.The biomarkers were bounded on the asphaltene with specific carbon position respectively.The high ratios of gammacerane carboxylic acids to C₃₀ hopanoic carboxylic acids and a complete series of 4-methyl,4,4-dimethyl steranoic acids indicated that the oil is a mixing oil originated from Es⁴ and Es³ source rock.The low isomerization of the biomarker acids showed that the maturity of the oil is low.Ruthenium-ions-catalyzed oxidation of the asphaltene provided a new pathway for the oil-oil correlation and oil-source correlation of heavily biodegraded oil.