Abstract: Based on the pyrolytic simulation experiment,the vitrinite's hydrocarbon-generation in coal related to its starting maturation. If the first hydrocarbon-generation is end and the maturation (starting maturation of the rehydrocarbon-generation) has not been exceed the oil-forming peak(R=0.9%), the rehydrocarbon-generation can greatly increase the potential of hydrocarbon-generation of coal, and when the starting maturation locate at oil-forming peak stage, the potential of hydrocarbon-generation is the biggest. Contrasting the three types of organic macerals in coal, the exinite of hydrocarbon-generation is the greater, the vitrinite is second and the inertinite is the least.