The physico-chemical properties of four samples of bentonite collected from Jiutai in Jilin Province, Changwei in Shandong Province and Nanjing in Jiangsu Province were studied. X-ray diffraction and chemical analysis of these samples were made and their particle size distribution, viscosity and cation exchange capacity were determined. Results obtained showed that all these bentonitea were Ca-Mg clays. The sample eollteted from Nanjing had a higher exchange capacity and that from Jiutai contained more exchangeable sodium.