A terahertz (THz) broadband polarizer using bilayer subwavelength metal wire-grid structure on both sides of polyimide film is simulated by the finite-difference time-domain method. We analyze the effect of film -thickness, material loss, and lateral shift between two metallic gratings on the performance of the THz -polarizer. Bilayer wire-grid polarizers are fabricated by a simple way of laser induced and non-electrolytic plating with copper. The THz time-domain spectroscopy measurements show that in 0.2–1.6 THz frequency range, the extinction ratio is better than 45 dB, the average extinction ratio reaches 53 dB, and the -transmittance exceeds 67%, which shows great advantage over conventional single wire-grid THz polarizer.