Abstract.  A narrowband terahertz (THz) filter based on metal–dielectric–metal structure with a circular loop array patterned on metallic films was proposed. The transmission properties in the THz range of the structure were experimentally and theoretically analyzed. The structure’s transmission spectrum has two narrow bands of which band 1 in the lower frequency range was dominated by the transmission mode due to localized plasmon polaritons and band 2 in the higher frequency range was dominated by propagated plasmon polaritons mode and guided mode. Both band 1 and band 2 have high $Q$-factors. By designing an asymmetry periodic constant in orthogonal directions, band 2 exhibits potentials as a narrowband polarizer. Furthermore, the transmittance of band 2 can be promoted to 100% by laterally shifting the metallic arrays.