There has been a great controversy over primary oil and gas reservoirs in the Meso-Neo Proterozoic. Meso-Neo Proterozoic primary reservoirs have not been found in China yet. Such findings will make a breakthrough in petroleum exploration of Meso-Neo Proterozoic. Abundant oil reserves have been found in the Meso-Neo Proterozoic of Damintun sag, which were considered as a type of young bed for source and old bed for storage. But in this study, the crude oil in the Meso-Neo Proterozoic reservoirs is different from that in the 3rd member of Shahejie Formation which indicates that other oil sources may exist. The Meso-Neo Proterozoic source rocks in the Damintun sag were studied and the result shows that they have high abundance and good type of organic matter, as well as a moderate degree of thermal maturation and a great potential of hydrocarbon generation. These all indicate that it may be an important oil source for the oil reservoirs in the Meso-Neo Proterozoic. The thermal simulation results of carbonate source rock samples show that the Meso-Neo Proterozoic source rocks have a good capacity of hydrocarbon generation.