Silicon　nitride　(SiN)　is　an　ideal　material　which　is　compatible　with　complementary　metal-oxide-semiconductor　(CMOS)　technology.　Its　advantages　include　suitability　for　high　power　handing,　a　large　spectral　range　and　low　thermo-optic　coefficient,　etc.　A　polarization　beam　splitter　(PBS)　is　one　of　the　significant　polarization　handling　devices　for　integrated　silicon　photonic　circuits.　In　this　paper,　a　low　insertion　loss　(IL),　broadband　and　high　extinction　ratio　(ER)　PBS　with　a　compact　coupling　length　of　6　μm　based　on　an　asymmetrical　directional　coupler　(ADC)　was　proposed.　It　consists　of　a　fully-etched　silicon　(Si)　strip　waveguide　and　a　silicon　nitride　(Si3N4)　strip　waveguide　with　a　vertical　gap　of　100　nm.　By　carefully　optimizing　the　parameters,　the　input　transverse　magnetic　(TM)　mode　polarization　from　the　Si　waveguide　will　couple　to　the　Si3N4　waveguide　due　to　the　phase　matching,　while　the　input　transverse　electric　(TE)　mode　polarization　will　keep　propagating　in　the　silicon　waveguide　due　to　the　large　refractive　index　difference　between　the　two　waveguides.　For　the　TE　polarization　mode,　the　simulation　results　show　that　the　IL　is　less　than　0.23　dB　and　the　ER　is　higher　than　56　dB　in　the　wavelength　range　of　1300-1900　nm.　For　the　TM　polarization　mode,　the　numerical　results　show　that　the　IL　is　less　than　1　dB　and　the　ER　is　higher　than　12　dB　in　the　wavelength　range　of　1424-1712　nm.　Meanwhile,　our　design　also　has　high　fabrication　tolerance　and　is　suitable　for　production　on　commerical　foundry.　©　2022　SPIE.