A reflective-type infrared filter is proposed based on a two-dimensional periodic micro-structure of circular aluminum disc-circular silica disc-aluminum substrate. Its infrared spectral reflectance is numerically simulated by finite element method. The simulated results show that this micro-structure exhibits excellent spectral filtering over 4~11 μm spectral range which is tunable, insensitive to TE or TM polarization and incident angles over 0 to 60°. The extraordinary infrared reflectance is deciphered with the plasmon polariton resonance theory, upon which a multilayered nanoring structure is proposed for further tuning to longer wavelengths and better absorption efficiency.