Abstract: Base on the combination of total porosity measurement and high-pressure mercury injection for shales, a quantitative study method focusing on shale’s pore structure and pore connectivity is established in this paper. The paper compares the total porosity, effective pore diameter distribution and pore connecting rate among the massive mudstone, laminar shale and laminated shale of Paleogene Shahejie formation in Dongying depression. The study shows that the massive shale has the lowest porosity ranging from 2.7% to 4.5%, laminated shale has the highest porosity ranging from 10.2% to 17.7%, and the porosity of the laminar shale is 5.9%~11.2%. The massive mudstone is dominated by pores of small pore diameter with the the main peak value less than 10.0 nm. The pore diameter of the laminated shale ranges from 3.6 to 10 000.0 nm with the main peak higher than 10.0 nm, and the proportion of pore diameter less than 10.0 nm is relatively low. The pore diameter of the laminar shale is distributed between those of massive and laminated shales, its main peak value is usually about 10 nm, the proportion of the pores with the diameter less than 10.0 nm in the laminar shale is lower than that of the massive mudstone, and the proportion of the pores with the diameter higher than 100.0 nm in the laminar shale is lower than that of the laminated shale. The massive mudstone has the lowest pore connecting rate, the laminated shale has the highest pore connecting rate and the laminar shale has the medium rate. The differences of the shale’s pore structure characteristics are related to sedimentary lithofacies and diagenesis. There are a few primary and syngenetic pores in the massive mudstone, which is not good for the formation of secondary pores. The pore structures of laminar and laminated shales are favorable for the preservation of primary pore and the formation of secondary pore