The Lower Es3 shale of Zhanhua sag is considered as good source rock and storing hydrocarbon, and its lithologic characteristics is entirely studied in this paper. On the comprehensive analysis of the core observation,thin section identification, SEM analysis and fluorescence reaction features, the lithologic type is classified and reservoir space is identified. The reservoir property is studied with reservoir space identification and core measurement of porosity & permeability. The research shows that: the shale is rich in calcite, with the depth getting deeper, the calcite content is increasing, clay minerals and quartz contents are decreasing; the laminated argillaceous limestone is the dominant lithologic type, and the first-rate type is composed of recrystalized calcite and clayey lamina; the reservoir space is consisted mostly by micro-fracture, intercrystal micropore of calcite and clay minerals; the porosity is predominantly ranged in 2% -8% and permeability 0. 1×10-3 -10×10-3 μm2 。