Abstract: A film design method based on genetic algorithms was proposed and the genetic algorithms for the design of film system were programmed in order to research the global optimization methods of the optical film system design. It was applied to the optimal design of various kinds of antireflective films. The results show that the antireflective films obtained by genetic algorithms are better than or equal to those published previously in spectral characteristics and overall performance. The optimal coating design with genetic algorithms can set the thickness limit and the number of layers without providing any initial film system. All the features are very favorable in both design and deposition of films. Furthermore, the method can be easily applied to the design of other optical coatings by changing the target reflectance values.