A tunable filter based on a metal-insulator-metal (MIM) nano-cavity waveguide is constructed by using side-coupled method, which consists of an arch-type resonator and a rectangular waveguide. The transmission characteristic spectra, resonance wavelength distribution and magnetic field distribution of the arch-type cavity waveguide MIM structure filter have been numerically simulated and analyzed by finite element method (FEM). The results show that the arch-cavity filter has smooth transmission spectra, flat passband with transmittance of 0.976, stopband with transmittance of 0.001 and wide bandwidth,which shows that this structure filter has good filtering characteristics. By optimizing the parameters of the type structure filter, the channel selection filtering function can be realized in three communication windows of the optical communication band. This structure filter has great application prospects in high-density optical integrated circuits and nano-optics.