Nanoporous metals are characterized by networks of interconnected ligaments and highly porous structure maintaining their high electrical conductivity. Due to their highly porous structure and interconnected ligaments, the specific surface area and the diffusivity within the nanoporous metals are significantly enhanced . These features of nanoporous metal facilitate remarkably increased chemically active sites and the mass transfer of reactants from exterior surface to interior structure. Hence, nanoporous metal structure has been applied to multifarious energy and environmental application such as fuel cells , supercapacitors [3,4], electro-catalysts . Currently, most nanoporous metal structures are fabricated using methods such as de-alloying [4,5,8-10], self-assembly , template . In particular, de-alloying is the most widely used method which can be extensively applied to various metals such as gold , silver , copper , palladium , platinum . However, for de-alloying technique not only using harsh, perilous reaction is required, but also the at least 50 atomic% a different kind of metal sacrificial template is required, which is great limitation for the practical use of de-alloying method in actual industrial application. Here we report a novel facile synthesis method for fabricating a nanoporous silver structure by electro-reduction of silver-silver bromide composite with tunable pore and ligament sizes (50-200nm). We systematically characterize the morphology and chemical composition of our nanoporous silver structure, and provide a detailed mechanism on the formation of sponge-like nanoporous silver structures.