This study focuses on acid activated beidellite and its adsorption ability for the herbicide simazine. After acid activation, the non-silicon atoms, such as Al, Mg, and Fe, which are located in the octahedral sheet, and sodium ions between the clay mineral layers were leached from the parent clay mineral. The basal spacing increased after acid activation. The acid activated beidellites were used to remove simazine from water. The simazine molecules can enter into the destroyed alumino silicate interlayer spaces and can be adsorbed from contaminated water.