Abstract: The Zha-X well area in the Qaidam Basin, Qinghai is currently interpreted as the main production area in the Zhahaquan block, and also an important potential area for the future production. The integrated studies show that the IV oil reservoirs of the Pliocene Xiayoushashan Formation in the Zha-X well area have mesoporosity and moderate to low permeability and are assigned to the anadiagenetic A stage. The diagenetic types include compaction, cementation and dissolution. The compaction may exert the limited effects on the physical properties of the reservoir rocks. The cementation is responsible for the decrease of the porosity of the reservoir rocks while the dissolution may have constructive effects for the generation of the secondary porosity of the reservoir rocks in the study area.