The invention discloses a single part used for a fuel cell. The single part is a multi-phase and multi-component composite film, wherein the composite film comprises five components of polyvinyl alcohol, anion exchange resin, perfluorosulfonate resin, a transitional metal oxide and a transitional metal hydroxide, wherein the polyvinyl alcohol and perfluorosulfonate resin are mixed uniformly to form a film substrate; the anion exchange resin is embedded in the film substrate in a granular way; and the transitional metal oxide and the transitional metal hydroxide are uniformly dispersed in the film substrate in a nanoparticle form. The invention also discloses a preparation method for the single part; a gel film coating method is adopted; the preparation method is simple and easy to control, and suitable for large-scale application; the single part provided by the invention is assembled with a flow field, a clamping plate, a pipeline and other auxiliary parts to form the fuel cell; the fuel cell can realize power generation to the outside by pumping fuel and oxygen; and therefore, the single part can replace a positive electrode-electrolyte film-negative electrode sandwich structure of the conventional fuel cell, so that the battery and the production assembling process can be greatly simplified.