Abstract: Mid-infrared integrated polarization focal plane detection technology, which combines polarization detection technology and mid-wave infrared focal plane imaging detection technology, has realized the monolithic integration of polarization grating and detector through heterogeneous integration, and has the advantages of small size, light weight, high mechanical stability and simultaneous imaging of multiple polarization directions. Pixel-level sub-wavelength metal gratings can achieve high extinction ratios in different polarization directions. However, the selection of metal material and the structural parameters of gratings such as pitch, duty cycle and thickness have a significant impact on the polarization performance. The theoretical analysis of the sub-wavelength metal grating was given, and the polarization performance simulation model of the mid-wave infrared integrated polarized HgCdTe detector was established, and the effects of different grating parameters on the polarization performance were analyzed. The optimal structural parameters of 200-400 nm Al grating pitch, 0.5-0.7 duty cycle, and over 100 nm thickness were determined by simulation. The simulation results show that the range of ±14° incident angle had a small effect on the polarization extinction ratio. Meanwhile, Si-based HgCdTe detector had been introduced. The influence of SiO₂ antireflection film thickness on polarization extinction ratio had been simulated to determine the optimal thickness. Compared with Cadmium Zinc Telluride (CdZnTe) substrated polarization HgCdTe detectors, the polarization performance of Si-based detector has been proved better. The simulation results can provide theoretical guidance and reference for the design of the polarization grating of the mid-wave infrared integrated polarization HgCdTe detector.