Bacteria are widely used for studying the heavy metal biosorption recently.In the study,the removal rate of Mn2+ under normal concentration and law of biosorption about Mn2+ using PCC 7120 were obtained.The results showed that a high desorption efficiency (above 80%) was obtained under the low concentation (10 mg/L) of Mn2+.The biosorption equilibrium data are fitted well with the Freundlich adsorption isotherm and kinetic studies,indicating that the biosorption follows the pseudo secondorder model.The tolerance of PCC 7120 to Mn2+ is impaired and the adsorption capacity is greatly diminished after nitrogen deficiency.