Based on thin film optics and laser technology,the use,design and preparation methods of coatings of broadband polarized separator in middle infrared lasers are reported.Based on the principle of wave optics,the polarization characteristics of core components ZnSe crystal and difficulties of broadband polarization beam splitter are first analyzed,then the main technical problems in the process of the Brewster angle incidence film selection,pass band broadening,and other studies are discussed.After computer optimization,combined with ion-assisted,low absorption，high polarization ratio,excellent anti-laser performance and adhesion of the coatings are obtained.Related technologies currently used in the mid-infrared solid-state lasers have achieved greater than 15W output power under 5kHz.