Abstract: The application of genetic algorithms to the film system design of narrow-band filter is studied. The operation principle, adaptability function and function parameters of genetic algorithms have been introduced. Merit and adaptability function of narrow-band filter have been founded, The way on program design of narrow-band filter has been given. As example, the film system of narrow-band filter with center wavelength of 1.55 μm and bandwidth of 4 nm has been designed practically by genetic algorithms. Results have showed that the genetic algorithms much fit the design on film system of narrow-band filter.