Abstract: The pore structure has an important influence on oil and gas seepage and productivity, and is also important for classification of low porosity and permeability reservoirs. In terms of micro scale, thin section observation and laboratory testing are used to describe the reservoir. In terms of macro scale, there is lack of an effective quantitative characterization method. In this paper, fractal theory is introduced into the evaluation of pore structure, and the relationship between porosity, permeability, displacement pressure, median radius of pore throat and fractal dimension is obtained with the established relationship between mercury injection data and fractal model. The results show that fractal dimension has a good correlation with reservoir physical properties and pore structure. It is feasible to use fractal dimension as a macro scale parameter to quantitatively characterize the complexity of pore space. At the same time, it may provide reliable quantitative characterization parameters for the classification of the reservoirs with medium to low porosity and permeability, and make a better decision-making basis for oilfield development and production.