Abstract: A comprehensive study is made in this paper on the lithology and depositional characteristics of the low-resistivity oil reservoirs of the Guanxi section of Guantao Formation, based upon the seismic, logging, and coring data and laboratory testing data collected from the QHD oil field of the Bohai Sea. The reservoirs in the Guanxi section is dominated by lithic feldsparthic sandstone and feldsparthic lithic-sandstone, consisting of subangular and sub-rounded sand deposits with gravels in an ordered sequence from medium-sized cross bedding, trough-shaped cross bedding, plate-shaped cross bedding, wavy cross bedding, to horizontal bedding from bottom to top. The mudstone is mainly variegated, which also indicates a shallow water environment under weak oxidation-weak reduction and/or oxidizing environment. In general, the low-resistivity reservoir suggests a weak hydrodynamic environment, dominated by such microfacies as braided channels, mid-channel bars, flood plain and small gullies. The integrated study suggests that sedimentary environment, diagenesis and micro-clay minerals are the reasons which caused the poor physical properties of the reservoirs and the complicated pore structure, which made up the high water saturation of the Guan Xi section is also a major factor for the formation of the low-resistance oil reservoirs.