Abstract: In this paper,the on-line analytical technology of gas chromatography-isotopic mass spectrography(GC/C/MS)of crude oil monomic hydrocarbons is applied combined with the discussion on the carbon isotopic distribtition of crtide oil monomic hvdrocabons to make preliminary genetic classification according to the sedimentary environments of their source rocks,This can yet be regarded as an efficient method in the oil-oil and oil-source rock correlations.