In　this　work,　we　fabricated　a　metacomposite　using　magnetorheological　fluid,　in　which　Fe　nanoparticles　dispersed　in　silica　gel　spontaneously　aligned　under　a　magnetic　field　to　form　chain-like　grids,　thus　working　as　a　wire-grid　polarizer.　A　single-layer　polarizer　was　fabricated　by　mixing　silica　gel,　silicone　oil,　high-purity　spherical　Fe　powder　with　about　100　nm　in　diameter,　followed　by　spin-coating　and　curing　the　mixture　under　a　uniform　magnetic　field　to　form　a　solid　matecomposite　layer　on　a　Teflon　substrate.　The　polarizer　was　characterized　by　terahertz　time-domain　spectroscopy,　showing　good　anisotropy　and　polarizing　characteristics.　Its　performance　was　improved　by　multiple-layer　stacking.　The　extinction　ratio　and　degree　of　polarization　of　a　five-layer　polarizer　are　above　20　dB　and　0.95　respectively　in　a　frequency　range　of　0.8-2　THz.