Abstract: Montmorillonite is characterized by small particle size, large specific surface area and strong water sensitivity, which results in blocking the pore and throat of the reservoir and in turn affecting its quality. Dissolution characteristics of montmorillonite under alkaline conditions are common concerns in the development of oil fields. Mass contrast, X-ray Diffraction, solution concentration analysis and value analysis of pH methods are commonly used to characterize dissolution of montmorillonite. However, the quality comparison method is complex. Calculation of diffraction pattern by the X-ray Diffraction involves large manual operation errors. The ion concentration analysis method shows a large detection error for infusible elements. Value analysis of the pH method is influenced by temperature changes. The specific surface area, pore volume, pore diameter change, adsorption-desorption curve measured by nitrogen adsorption method was used to characterize the dissolution of montmorillonite under alkaline conditions and is reported in this paper. The experimental conditions were optimized, including the concentration of NaOH solution and filling time (reaction time). The best concentration of NaOH solution was 0.05 mol/L and the best reaction time was 3 h. Results show that the dissolved results of montmorillonite by the nitrogen adsorption method characterized by specific surface area, pore volume, pore diameter and adsorption desorption curve are consistent with the results by the change of the pH value and the concentration of the solution (such as Si⁴⁺). Therefore, the method is feasible and can be used to characterize the dissolution of minerals with multiple pores and large specific surface area.