To solve the polarization-ralated losses and polarization mode dispersion problems of silicon on insulator platforms and to improve the efficiency of polarization diversity systems, this paper proposed a polarization beam splitting-rotation-multiplexing integrated device based on Asymmetric Directional Coupler (ADC) and Subwavelength Gratings (SWG) with a thick silicon core layer is proposed, which can convert any input light into a output light of Fundamental Transverse Electric (TE₀) Mode. The integrated device consists of three parts: polarization beam splitter, polarization rotator and wave combiner. The Three-Dimensional Finite Difference Time Domain (3D-FDTD) method is used for simulation analysis, and the structural parameters are optimized. The size of the device is 4.5 ●x03BC;m×56.0 ●x03BC;m. At the input wavelength of 1.55 ●x03BC;m, it has a high polarization extinction ratio of 45 dB, and an insertion loss of 0.53 dB. A bandwidth of 75 nm is achieved when the polarization extinction ratio is greater than 30 dB and the insertion loss is less than 1 dB. Therefore, the operating frequency range of the device can cover the entire C-band. Finally, the influence of process error on device performance is analyzed. The integrated device has a compact structure and a higher polarization extinction ratio, which can meet the requirements of modern optical communication and optical integrated systems.