Nanoporous polymers with gyroid nanochannels can be fabricated from the self-assembly of degradable block copolymers, polystyrene-b-poly(L-lactide) (PSPLLA) after the hydrolysis of PLLA blocks.Well-defined nanocomposites with SiO2 gyroid nanostructures in a PS matrix can be obtained by using the nanoporous PS as template for sol-gel reaction.After the degeneration of the PS matrix, the nanocomposites can be transferred into inorganic double gyroid network with high porosity.The amorphous SiO2 with high porosity exhibits low refractive index (as low as 1.10) such that giving excellent antireflection property.