Simulation based on finite element method is carried out to investigate the transmission properties through subwavelength double layer metallic mesh in terahertz range.The mesh layer is composed of thin rectangular metallic plates arranged in period of about half wavelength.Under normal incidence,a resonant transmission peak enhances with the increasing ratio of area occupied by metallic plates to the area of the total surface.The surface plasmon plariton and pseudo Fabry-Perot model is presented for the interpretation of this anti intuitive result.