Abstract: 【Objective】To preparing sodium bentonite and investigate its adsorption characteristics to Cu(Ⅱ).【Method】The calcium bentonite was converted into sodium bentonite with sodium chloride as the conversion agent by suspension method. The adsorption characteristics of modified bentonite to Cu(Ⅱ) were conducted by fitting the adsorption isotherm as well as the influence of the acidity and temperature.【Result and conclusion】It was shown that the adsorption of modified bentonite to Cu(Ⅱ) conformed with the Freundlich pattern，which was a single molecular layer adsorption，with 90 min reaching to equilibrium，the lower acidity, the greater adsorption capacity. However, the adsorption capacity reached stability after pH＞5，the higher temperature, the smaller adsorption capacity，with the adsorption capacity remaining unchanged when the temperature was higher than 35 ℃. At the 25 ℃ and pH5，the removal rate reached 97.85% when 0.200 g modified bentonite was added to the 50 mL 10.0 mg/L copper ion solution. Results show that the modified bentonite can play an important role in the removal of copper ion.