Mesoporous birnessite-manganese oxide (b-MnO2) was studied for air electrode for Li-air rechargeable battery. In this study, mesoporous b-MnO2 with an average pore size of 3.52nm and BET surface area of 237m2 g−1 was successfully prepared using inorganic/organic phase. Prepared mesoporous b-MnO2 was applied for air electrode for Li-air battery and discharge capacity of 345mAh g−1 was observed at a current of 0.13mAcm−2. With the dispersion of small amount of Pd to mesoporous b-MnO2, it was found that the Li-air cell showed a reasonably large discharge capacity of 487mAh g−1 at 0.13mAcm−2 at the initial cycle. The first discharge plateau around 2.71V vs. Li/Li+ and charge plateau at 3.58V vs. Li/Li+ with highly reversible capacity were observed. The energy efficiency for the charge and discharge was estimated to be ca. 76.4%. The ex-situ XRD result of the mesoporous b-MnO2/Pd/TAB-2 (85/5/10) air electrode suggested that the observed capacity mainly came from Li+ and O2 to form Li2O2 after discharge to 2.0V. Formation of Li2CO3 was hardly observed.