In order to enhance transmission rate and mechanical intensity of ZnSe, the design and de- position of high performance infrared antireflection films on ZnSe substrate by ion beam assisted deposi- tion are discussed. The choice of films materials and the design of films system are introduced.The mea- sured spectral curve of 8～12 μm wavelength range antireflection films deposition by this method has been given. The experimental results show that the films have good characteristics such as a peak transmi" ssion of more than 99%,an average transmission in the designed wavelength range of greater than 98%, good adherence and stability of optical and mechanical properties. These are important for the application of infrared optical system.