The design approach of the transmission filter using the subwavelength metal waveguide grating with narrow grooves is proposed.The operational principle of the filter is that its low transmission background is obtained by using the metal grating with narrow grooves

and its transmission peak is achieved by using the hybrid Guided-Mode Resonance（GMR）and the Surface Plasmon Polariton（SPP）resonances.It is shown that by increasing the thickness of the waveguide layer

a dual-channel transmission filter with good filtering performance can be obtained based on the hybrid modes of multiorder GMR and SPP resonances.The transmission peaks of the dual-channels at 1 412 nm and 1 653 nm are 72.1% and 63.6%

respectively.Further analysis show that the peak transmission and its location of the filter at longer wavelength is mainly affected by the grating thickness.This is because that the energy of the magnetic field of the longer wavelength is mainly confined in the grating layer.For the transmission peak of the filter at the shorter wavelength

the energy of the magnetic field is mainly confined in the waveguide.Therefore

the shift of the transmission peak is sensitive to the variation of the waveguide thickness.