Gu’nan is one of rich oil-gas subsags of Zhanhua depression. This paper, in order to clarify its exploration potential, analyzes the Tertiary sedimentary sequences characters, oil-formation parameters and reservoir-forming conditions, re-evaluates its resource. According to the hydrocarbon discharge and aggregate, Gu’nan subsag has a potential of 50-60 million tons. This paper discusses the sandstone body development and reservoir-forming conditions, presents that Gu’nan subsag has several reservoir-caprock combinations, excellent oil-gas transfer channel and traps, which form a special oil-gas rich zone, and determines the favorable target areas.