Abstract: The potential of hydrocarbon generation of Eogene source rock in Damintun depression. Liaohe oilfield, were systematically studied. Among them the type III organic matter is of following several features. Firstly, the maturation rate of it is slow. An increment of 1000m in burial depth only corresponds to an increment of 0.2% in vitrinite reflectance according to the regressive equatiion. So the oil generation zone of the source rock is very wide. Secondly, no obvious relationship between the group section of the liquid products of thermal simulation and the evolution degree of the organic matter exists. The products is rich in resin and asphltene. This is similar to that of bitumen A of the source rock. Finally, no remarkable difference of the potential of hydrocarbon generation appear at different evolution stages. No obvious stages and peak of hydrocarbon generation occur. The period of hydrocarbon generation last quite long. The deadline of oil generation is beyond R0 = 2%. All of the features mentioned above show that type III source rock in Damintun depression is of a really peculiar pattern of hydrocarbon generation, which differs from the traditional ones.