Along with the development of oblique angle deposition and etching, the development of reflection coatings has been broadened by the nano-porous low-index material, which has played an important role in reducing the reflection of the wide-angle incident light and maintaining the color balance. An optimized four layers graded-index antireflection coating on H-K9L optical glass with broadband and omnidirectional characteristics designed by genetic algorithm is presented. The reflection coefficient curves are also obtained and compared with the single layer made by normal materials. It plays a very good role in reducing reflectivity for the visible light when the incident angle ranges from 0° to 75°. The total average wide-angle visible spectral reflectivity can be reduced to 0.21% in this scope.