Abstract: The bulk-rock analysis technology of organic petrology was used in this paper to systematically study the maceral composition, hydrocarbon-generating components and organic thermal-evolution of the Lower Tertiary source rock in the Jianghan Basin. The morphologic maceral content of source rock in the Jianghan Basin is apparently on the low side. On an average, it only takes 1.5 percent of the whole rock volume. Sapropelite is rich in the maceral composition, vitrinite and exinite are relatively developed, and inertinite is poor. The organic matter is dominated by Ⅱ and Ⅰ types. Alginite and mineral bituminous matrix are the main hydrocarbon ge nerating componets of this area. By using vitrinite reflectance and the fluorescence parameters of hydrogen enriched components and non hydrocarbon fractions, the evolutionary characteristics of organic matter in the source rock of the Jianghan Basin were discussed, and the classification scheme of thermal-evolutionary stages for the organic matter was suggested.