A high-performance polarizing beam splitter is designed based on Al_0.9Ga_0.1As/Al₂O₃ subwavelength grating in this paper. The polarizing beam splitter is alternately formed by using Al_0.9Ga_0.1As and Al₂O₃, the preparation is simple, and the structure is stable and easy to integrate. The relationship between the reflectivity, duty cycle and period of the grating is analyzed by the rigorous coupled wave analysis method. By selecting the appropriate grating parameters, the grating structure can achieve different diffraction characteristics of transverse electric (TE) and transverse magnetic (TM) polarized light, and the polarization beam splitting function is realized. The simulation and calculation results show that in the wide spectral range of 80 nm (800-880 nm), the reflectivity of the grating polarization beam splitter for TE polarized light is greater than 94%, the transmittance of TM polarized light is greater than 90%, and the polarization extinction ratio is greater than 10 dB, up to 41.37 dB. In addition, the effects of grating parameter variation and incident angle deflection on the performance of the polarizing beam splitter are also investigated. The results show that the polarizing beam splitter has good process tolerance and can tolerate 4° of left and right deflections for vertical incidence, which effectively solves the problems of difficult integration and complex fabrication of traditional polarizing beam splitters, and can be combined with GaAs-based devices. After integration, the control of the incident beam is realized.