In order to couple merits of two dimension and porous materials, by using unique solvent free method, the mesoporous layered alpha-MnO2 structured by 2 nm nanosheet was successfully synthesized, which possesses ultra-high surface area (339 m(2) g(-1)), meso pore size of 6 nm and large amount of oxygen vacancies. When serving as a cathodic oxygen reduction reaction catalyst in microbial fuel cell, it exhibits superior electrocatalytic performance comparable to the commercial Pt/C and achieves the maximum power density of 1671 +/- 26 mW m(-2) with a exchange current density of 21.18 A cm(-2). Meanwhile, density functional theory study reveals that the obviously shrinking of forbidden band and the pseudo band gap between two sharp peak of d DOS, which results in an excellent electrical conductivity, efficient electron transport and low overpotential of electrode. Therefore, it can be expected that the as-prepared MnO2 catalyst, with extraordinary electrocatalytic performance through a combination of the ultrathin nanosheet architecture and oxygen vacancies, is promising and produces high power density in microbial fuel cell.