Abstract: The Jurassic Toutunhe formation in WellBlock Shinan-4 of Shixi Oilfield is the braid-like sedimentary river delta. From the bottom to the top, the sedimentary sequence is lake level first descending and then quickly rising, thus formed a set of terrigenous clastic rocks. Middle sandstone and mudstone are dominant at the bottom, coarse and medium sandstone facies in the middle, and thick massive mudstone at the top. Through analyzing the data of rock slice, cast thin section, scanning electron microscope and X diffraction, this paper studies in detail the characteristics of rock and ore, pore structure and physical properties of the reservoir in the study area. The results show that the rock types of reservoir in Toutunhe formation are mainly lithic sandstone. The cementation is mainly carbonate cementation, and the main type of cementation is porous cementation. The hetero-group is mainly argillaceous. The clay minerals are mostly kaolinite, and the contents of kaolinite and chlorite are positively correlated with reservoir porosity. The reservoir has the characteristics of strong alkali sensitivity and moderately water sensitivity. The types of reservoirs are primary pore and secondary pore. The primary pore is mainly intergranular pore associated with quartz and chlorite minerals; the secondary pore is mainly intergranular solution pore associated with feldspar and high-collar minerals. The reservoirs belong to medium porosity and low permeability reservoirs. Based on the reservoir characteristics and main controlling factors of sedimentary microfacies, the reservoir sand bodies of Toutunhe Formation is divided into high quality reservoir type I and reservoir type II. At the same time this paper predicts the favorable reservoir areas and identifies the favorable potential areas. The potential areas can be the key areas in the follow-up progressive development of WellBlock Shinan-4.