CuO modified hollow SnO2 nanofibers with large specific surface area were successfully synthesized via a simple two-step process, using the electrospinning method and hydrothermal technique. Gas-sensing experiments on hierarchically CuO modified SnO2 hollow nanofibers displayed higher sensitivity and selectivity to H2S gas at lower operating temperatures compared with unmodified hollow SnO2 nanofibers. At the optimal operating temperature of 125 degrees C, the highest response value to 10 ppm H2S gas reached 410. Response time decreased when the concentration of H2S increased. It is almost no response to other gases when the operating temperature falls below 200 degrees C. The specific interaction between H2S gas and the CuO nanoparticles, as well as the amplifier effect on the gas response by the p-n junctions, strongly enhances the selectivity to H2S gas at a lower operating temperature.