Catalysis using gold (Au) nanoparticles has become an important field of chemistry. However, activity loss caused by aggregation or leaching of Au nanoparticles greatly limits their application in catalytic reaction. Herein, we report a facile and green synthesis of a core-shell Au@SnO2 nanocomposite, exhibiting excellent activity toward selective nitroaromatics reduction under mild conditions. The core-shell Au@SnO2 nanocomposite (Au size = similar to 50 nm; shell thickness = ca. 16 nm) is conceived and validated by a direct redox reaction between HAuCl4 and SnF2. Optimization of the core size, shell thickness, and dispersion of Au@SnO2 has been introduced by an alkaline surface supported by negatively charged metal oxide Na2Ti4O9. The as-obtained Au-Sn-Na2Ti4O9 catalyst with much smaller Au cores (ca. 5 nm) and thinner SnO2 nondensed shells (ca. 4 nm) exhibits highly improved catalytic activities for nitro reduction compared to most of the known Au-based catalysts. Moreover, the core-shell Au@SnO2 structure inhibits the leaching and agglomeration of Au nanoparticles and thus leads to superior catalytic durability.