Abstract: Regarding the classification and determination of swelling potential of expansive soils,variations are observed among different sectors and geographical areas. Generally,the free swell ratio serves as the primary criterion for determination,with the montmorillonite content serving as supplementary verification when required. However,differences persist between these two methods in evaluating the swelling potential. This study undertook a comparative analysis of the swelling potential determination methods for expansive soils in a certain region of Southwest China,utilizing both the free swell ratio method and the methylene blue adsorption method to ascertain montmorillonite content. This study delved into the causes of the observed differences. By refining the experimental operation,this study improved the experimental method and enhanced the accuracy of the montmorillonite content measurement. Subsequently,leveraging the swelling potential results derived from the free swell ratio method and integrating the physical and mechanical characteristics of the expansive soils in this region along with practical engineering insights,this study proposed recommendations for adjusting the threshold values used to evaluate swelling potential based on montmorillonite content. These adjustments aim to align the swelling potential determination conducted via the methylene blue adsorption method with that obtained through the free swell ratio method,thereby providing a valuable reference for engineering professionals.