The composite technique of templating and dealloying is proposed for synthesizing the low-density and hierarchical nanoporous gold (NPG). In this technique, the silica (SiO2) microspheres with an average diameter of ~700 nm are prepared as the sacrificial templates, the Ag@SiO2 and Au@Ag@SiO2 core-shell microspheres are prepared successively via the electroless plating approach, and the Au@Ag@SiO2 alloy bulks are formed through the cold-pressing and sintering method. By continually changing corrosion solutions, the templates and the Ag element can be completely eliminated from the Au@Ag@SiO2 alloy. The SiO2 templates are completely removed from Au@Ag@SiO2 microspheres so as to form the large-sized hollow spherical shells (with the diameter of ~675 nm), and the Ag element are eliminated by dealloying so as to generate a lot of small-sized pore (with the diameter of ~75 nm) structures on the shells. TEM images illustrate that the ligaments in NPG consist of the nano-grains with polycrystalline characteristic. The hierarchical NPG foam with low-density of 1.1 g/cm3 (the relative density of ~5.7 %) and high surface area of 4.24 m2/g shows the excellent catalytic activity and the rapid mass transfer rate for methanol electro-oxidation in alkali solution, which implies a promising application in catalysis.