Ag-doped porous SnO2 nanopowders were synthesized via a facile glucan-assisted template method combined with subsequent calcinations. Morphology, crystal structure, and H2S gas sensing properties of pure and Ag-doped porous SnO2 nanopowders were investigated. In comparison with undoped SnO2 nanopowders, the Ag-doped porous SnO2 nanopowders demonstrated enhanced H2S sensing behavior with high sensitivity, short response and recovery time, relatively low response concentration of 50 ppm, and good selectivity. The dramatic improvement in H2S gas sensing characteristics was explained in terms of rapid gas diffusion onto the entire sensing surface due to the less-agglomerated and porous structure of SnO2 nanopowders and the catalytic effect of doped-Ag element. The main objective of this research is to develop a new method to introduce catalysts on gas-sensing materials with less-agglomerated and porous structure.