Various polymorphs of MnO2 were synthesized with a controlled hydrothermal method.Li-Mn-O precursor was prepared by the wet impregnation of a solution of LiOH·H2O into MnO2 synthesized，and the final MnO2 ion-sieve was obtained by acid treatment.The crystalline phase structure and exchangeability of Li+were studied with XRD，TEM Li+adsorptive isotherm and kinetic measurement.The result showed that reactant concentration had different effects on the growth rate of different MnO2 crystal faces.The novel MnO2 nanowires，mainly about φ 5 nm×400 nm in diameter and length，were found to have a remarkable lithium ion sieve property with monolayer saturation amount of 2.43 mmol·g-1 and the adsorption rate constant of 2.16×10-6s-1 at pH=9.19.The lithium adsorption capacity of MnO2 ion-sieve increased with the increase of pH value，up to 3.47 mmol·g-1 at pH=12.5.