Disclosed is use of a porous membrane and a composite membrane thereof in a redox flow batteries, and in particular the use thereof in a vanadium redox flow battery. The membrane can effectively realize the separation of ions with different valence states, and an ion transfer without any ion exchange group. The pore size and structure of the porous membrane can be controlled by filling an inorganic substance or grafting an ion exchange group in the pore, in order to improve the barrier properties of the porous membrane for vanadium ions and to increase proton conductivity.