A method for filtering gas includes providing a gas filtration structure, and the gas filtration structure includes a porous support and a first gas filtration film pair on the porous support, wherein the first gas filtration film pair includes a first hydrogen permeation layer and a first calcinated layered double hydroxide (c-LDH) layer, and the first hydrogen permeation layer is disposed between the porous support and the first c-LDH layer. The method also provides a hydrogen-containing mixture gas over the first gas filtration film pair, and collects hydrogen under the porous support.