In this work, Cu7S4-CuO microflowers were successfully synthesized through a simple hydrothermal route. The influence of S doping amount on the corresponding microstructures and gas sensing properties of the composites are investigated. In the comparative gas sensing test, the sensor fabricated from Cu7S4-CuO (S/Cu = 27 mol%) microflowers exhibited the highest response (156-50 ppm) to hydrogen sulfide with a fast response and recovery time. Furthermore, Cu7S4-CuO (S/Cu =27 mol%) microflowers gas sensor not only showed superior hydrogen sulfide selectivity compared with other gases, but also ppb-level detection limit (100 ppb-16.2) at 225 degrees C, even lower detection limit (50 ppb-1.8). The synergistic effects between CuO and Cu7S4, more surface adsorbed oxygen, and active sites were regarded as the main reasons for the ultrasensitive and selective hydrogen sulfide detection.