To improve the resistance of long wave infrared (LWIR) band antireflective films on Ge in harsh environments, film design and fabrication technology have been discussed using LaF3 as a low refractive index material. We fabricated high-performance multilayer antireflection (AR) coatings in an LWIR band (8–12 .m) via an optimized film structure and sectional preparation of LaF3 layer on Ge substrate. The peak transmittance was 98.3%, and the average transmittance increased from 48.4% to 96.2% when double-sided coating was used. This LWIR AR coating with LaF3 passed various environmental, durability, and mechanical properties tests while maintaining good optical properties.