Method for preparing solar selective absorbing coating

The invention discloses a method for preparing a solar selective absorbing coating. According to the method, quartz glass is adopted as a substrate, and a groove which is 500-600nm wide and 100-150nm deep is etched on the substrate by using the etching technology; six layers of metal/ceramic multi-layer gradient films with different components are deposited on the substrate provided with the groove by adopting a vacuum coating method; finally, a layer of Al2O3 antireflection layer is deposited on each metal/ceramic multi-layer gradient film by using a vacuum evaporation plating method. By adopting the substrate provided with the groove, light trap action can be generated on the sunlight, so that the solar absorptance of the film is greatly improved; meanwhile, a gradient coating is formed by heat-resisting metal W, Mo and the like, so that the heat resistance of the coating is greatly improved, and the requirements of a high-temperature coating can be met.