The development of high rate performance and low cost Ni-Zn battery is plagued by the shape change and dendrite formation of Zn anode material. Herein, through a controllable two-step method, a ZnO/graphene composite is prepared by an in-situ growth mechanism, in which ZnO nanoplates are vertical grown on graphene. In this unique structure, the sufficient contact between the vertical discrete nanoplates and electrolyte promotes ion diffusing greatly, balances the Zn deposition rate in the axial and epitaxial direction overall, and the flexible graphene buffers the associate volume change of Zn anode effectively, thus enhances electrochemical performance remarkably. We demonstrate a flexible quasi-solid-state Ni-Zn secondary battery using the as-prepared ZnO/graphene composite as anode material. This battery delivers a high specific capacity of 296.71 mA h g−1 based on the mass of ZnO/graphene and an outstanding cycle stability (86.69% retention after 400 cycles) at 5 mA cm−2 (1 A g−1), a quite high power density of 85.69 kW kg−1 together with a high capacity retention of 220.03 mA h g−1 at current density of 250 mA cm−2 (50 A g−1) based on the total mass of ZnO/graphene composite.