Advanced aqueous batteries with abundant global reserves, large discharge capacity and long life span are crucial research objectives. Herein, a kind of aqueous Zn-ion battery was fabricated with ultra-thin Ni-Mn nanosheet electrode and zinc foil. A simple H-annealing process was employed to handle the NiMnO nanosheets to form oxygen vacancy. Based on the formation of fast ion diffusion channels and the increase of active sites, the fabricated H-NiMnO nanosheet electrode displays an areal capacity of 0.68 mA h cm at a current density of 2 mA cm and an excellent cycling performance (almost no reduction after 6000 cycles). The fabricated H-NiMnO//Zn battery obtains a high areal capacity, up to 0.66 mA h cm at a current density of 4 mA cm, and shows a long cycling stability (88.5% capacity retention after 5500 cycles). In particular, it has a high energy density, up to 1.13 mW cm at a power density of 3.34 mW cm, more than many other similar devices. Thus, this research provides a new idea for the wide application of aqueous Zn-ion battery in intelligent equipment and electric vehicles.