A terahertz (THz) filter based on graphene/metal hybrid nanogratings is studied with the finite element method. Nanocavity arrays can be formed by the hybrid gratings. A THz filter is prepared by using the magnetic Fabray-Perot resonance effect in the nanocavity. The wavelength choice performance of this filter is unaffected by the external environments and the filtering wavelength can also be dynamically controlled. In addition, the filtering performance of this filter can be enhanced via the increase of the graphene layer number.