Abstract: The effects of magnesium hydroxide dose and pH value were investigated. The thermodynamics, kinetics and the mechanism for the adsorption of Cr(Ⅲ) on magnesium hydroxide were studied.The results show that magnesium hydroxide has a better adsorption capacity, the adsorption isotherm accords with Langmuir and Frendlich mode. The maximum adsorption amount is 69.44mg/g. The second-order kinetic equation can express the dynamics characteristics.