Abstract: In order to deeply study the adaptability of the fractal theory model to calculate the fractal dimension of the different size pores, with the drilling rock core samples of the shale in Longmaxi Formation from Jiaoye No.1 Well and the shale in Niutitang Formation from Ciye No.1 Well as the study objects, the CO2 and N2 isotherm adsorption tests were applied to get the micropore and mesopore adsorption data of the shale from the two formations. And individually to combine with the micropore fractal model and the FHH fractal model, the micropore and mesopore fractal dimensions were calculated. The efficiency of the two models was discussed. The study results showed that the micropore fractal model was suitable to calculate CO2 adsorption data and could effectively characterize the fractal dimension of micropore in shales. The FHH fractal model would be suitable to calculate the high pressure sectional data of the N2 adsorption and could effectively characterize the mesopore fractal dimension of shales. The micropore and mesopore could have different fractal structures. The evaluation of the shale pore structure should comprehensively consider the fractal dimensions of two type pores.