The porous structure of printing paper is an important influencing factor for the print quality and safety of food packaging paper materials. This work aimed to study the porosities and surface porosities of paper samples collected from 8 different domestic paper factories using the silicone oil saturation method and Image J image processing method. The porosities of the 8 paper samples were determined using silicone oil instead of the traditional benzene and absolute ethanol. Binarization processing of the SEM images of the 8 paper samples was conducted using the Image J image processing method, and the surface porosities were calculated by setting of threshold values and parameters. The porosities of the paper samples measured by the saturation method were between 40.20% and 59.52%, and the errors among parallel samples were lower than 6% . After saturation and drying, no discrete phenomenon occurred between the fibers of the paper samples. Meanwhile, the surface porosities of the paper samples determined by the image processing method were between 9.90% and 23.80% . The porosities of paper (board) samples werepositively correlated with their thickness, while the surface porosities were associated with the surface processing. The surface porosities of samples 3 and 8 were relatively low, which were 10.10% and 9.90% respectively, and the possible cause was the coverage of their surface pores by the coating.