Abstract: Abstract：The existence of rich organic matter constitutes one of the notable features of the Mayuan lead-zinc deposit in Shaanxi Province. In addition to the asphalt that can be identified by naked eyes and microscope, there occurs extremely abundant scattered organic matter whose composition needs to be analyzed by means of organic chemistry. Based on a microsection identification of rocks and minerals, an analysis of content and isotopes of the organic matter, and chromatography of saturated hydrocarbon gas, the author revealed the modes of occurrence and composition of organic matter in rocks, and concluded that the types of asphalt are syngenetic-diagenetic asphalt, epigenetic (remolded) asphalt and supergene asphalt. On the basis of such biomarkers as n-alkanes, pristane and phytane, the composition of the organic matter can be determined, the ore-forming environment can be analyzed, and the relationship between the organic matter and lead-zinc can be detected.