Near infrared filters and middle infrared band-pass filters have their important applications in aerospace, meteorology, remote sensing and other fields. An infrared filter is a device which can transmit infrared radiation and cut off the light at other wavelengths. The peak transmittance is its main performance index. For a band-pass filter, its important performance indexes include the peak transmittance and the half width of the passband. These performance indexes are most dependent on the film structures and specific design of the optical films for infrared filters. Both kinds of filters and their practical applications are presented.