Abstract: Through the analysis and the study of organic matter in coal measures, the geochemical characteristics and the composition of the organic matter are systematically expounded in this paper. Under thermal simulation experiments, the mechanism of the hydrocarbon generation of the organic matter in coal measures is also studied. It is suggested that the organic matter of coal measures differs significantly from that of oil source rocks both in origin and in original composition.The evolutionary processes of the organic matter of coal measures are devided into three stages, i.e. immature stage (prior to brown coal); mature stage (from flame coal to coking coal); overmature stage (lean coal-anthracite).