Attapulgite clay was soaked with natural brackish water, and the effects of soaking time on the viscosity, rheological and suspension stability of attapulgite were intensively investigated. The results indicate that the metal ions in the brackish water were exchanged with the surface ions of attapulgite, which altered the surface charges of attapulgite and thus improved its colloidal properties. After soaking for 90 d, attapulgite exhibits the best suspension stability. After soaking for 180d, the rotary viscosity of attapulgite was increased from 1188 mPa.s to 2444 mPa.s.