The present invention provides a nickel-zinc secondary battery, including: a battery case; an electrode assembly, disposed in the battery case; and an electrolyte solution, positioned in the battery case, and filled around the electrode assembly, wherein the electrode assembly includes a nickel positive electrode, a zinc negative electrode, and a membrane separator disposed between the nickel positive electrode and the zinc negative electrode; the nickel positive electrode includes: a substrate and positive electrode material coated on the surface of the substrate; the positive electrode material includes: 68 wt %˜69 wt % positive electrode active material, 0.6 wt %˜1 wt % yttrium oxide, 0.2 wt %˜0.6 wt % calcium hydroxide, 3.5 wt %˜4 wt % nickel powder, and a binder in balance; and the positive electrode active material is a spherical nickel hydroxide coated with Co3+. The nickel-zinc secondary battery provided by the present invention can reduce the amount of hydrogen evolved and have good cycling performance while maintaining the battery capacity. The present invention further provides a method for preparing a nickel-zinc secondary battery.