As the key components of the IR optical systems,infrared (IR) antireflection (AR) coatings are such important topic and the study of them are so complex. According to the demands of germanium(Ge)windows for the researching project,non-symmetrical equivalent layers theory are adopted to design the multilayer broadband AR coatings. The optical coefficients of the coating materials are fitted at established technics conditions and all the fitted optical coefficients are used in the layer thickness optimization process. A theoretical design approaching to the factual situation is obtained. After the optimization of the deposition technics,high performance broadband AR coatings are finished. The average transmittance of the spectrum tunnels such as 3.5-4.0 μm,6.3-7.6 μm,10.3-11.3 μm is more than 96% and the average transmiffance of the tunnel 11.5-12.5 μm is more than 94%. All the AR coatings can experience the environment tests and meet the optical system′s request.