The 193-nm immersion step-and-scan projection lithography tool is the most critical equipment in the high-volume manufacturing of integrated circuit with 45nm technology nodes and beyond. With the increase of numerical aperture (NA) of the projection lens, the resolution of lithography tool can be enhanced effectively. However, the polarization effect of the optics in an exposure system is more significant in high NA immersion lithography, which influences the lithographic imaging quality greatly. Thus, the polarization parameters of the immersion exposure system should be controlled -accurately for ensuring the lithographic imaging quality. With the advantages of miniaturization and high-accuracy online detection, the grating is applied to the polarization detection of the immersion lithography tools. A bilayer metallic grating polarizer with compact structure and excellent polarization performance is designed based on the inverse polarization effect and transmission enhancement effect on TE-polarized light. Rigorous coupled-wave theory and finite-different time-domain method are used to design the bilayer metallic grating polarizer. The former is used for analyzing the initial structure parameters of the grating, and the latter is used for acquiring the cross-sectional electromagnetic field of the structure. The initial parameters of the grating are calculated based on the surface plasmons resonance and Fabry-Perot-like theory. The influence of geometrical parameters of the grating on its polarization performance is analyzed. The simulation results show that the enhancement of TE-polarized light transmittance is mainly modulated by the middle layer height of the grating. Firstly, the TE-polarized light transmission is enhanced by the standing wave in the bottom medium cavity, and further enhanced by the top optical funnel formed. However, the transmission suppression of TM-polarized light is mainly caused by the low frequency mode of charge movement formed by surface plasmons. For the designed grating polarizer, the transmittance of TE-polarized light is 56.8%, and the extinction ratio is 65.6 dB at normal incidence. Comparing with previous metal grating polarizer, the extinction ratio of the designed grating is increased by four orders of magnitude.