The importance of MnOOH dispersion and interfacial contact between MnOOH nanowires and carbon black for the cathode of metal-air batteries has been clearly demonstrated from the textural, voltammetric, and electrochemical impedance spectroscopic (EIS) analyses. In comparing with the physically mixed composite, the MnOOH nanowires/XC-72 composite co-precipitated by hydrothermal synthesis shows much better performances of oxygen reduction in 1M KOH, which is attributed to the higher active surface area resulting from the better dispersion of MnOOH and the smooth electron pathways resulting from the higher interfacial contact surface area between oxide and carbon nanoparticles within the hydrothermally co-precipitated MnOOH/XC-72 nanocomposites. The absence of diffusion responses in the low-frequency range of EIS spectra reveals no/minor oxygen-diffusion effect at low overpotentials (E ≥−0.3V vs. Ag/AgCl).