In this study, a nano-sized MgO powder was synthesized by precipitation method and tested for the removal of reactive dye. The effects of MgO dosage, initial pH, contact time, and initial dye concentration on the dye removal were investigated. Results showed that as-prepared MgO powder can remove more than 99 percent of dye under optimum conditions of a MgO dosage of 0.1 g, initial pH in a wide range of 3~12, a contact time of 20 min, and initial dye concentration of 100 mg.l-1. The adsorption isotherms for reactive dye fit both Langmuir and Freundlich modes.