Based on the analysis of fractured reservoirs and petroleum geologic characteristics in Nanyishan Oilfield of Qaidam Basin, the paper concludes that the types of fractures can be identified as tectonic fracture, diagenetic fracture and abnormal pore fluid pressure fracture. Because the formation mechanisms of fracturesare different, the developmental degrees of the controlled fractures are different, too. Tectonic action is the main force causing fractures in the area; diagenesis influences, in a way, the generation and developmental degrees of fractures. Abnormal pore fluid pressure only accelerates the formation of fractures in deep reservoirs. The hydrocarbon accumulating combination belongs to the self-generation and self-store mode. Fracture belts and anticlinal axis fracture beltscontrol the distribution of fractured reservoirs. The fractured reservoirs distribute mostly in the effectively developed beds of dolostones and the transitional beds from dolostones to evaporates. 