Abstract Novel microgas sensors based on hollow and hierarchical copper oxide microspheres are fabricated and their gas-sensing properties are researched. The copper oxide microspheres are characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) after being annealed at 300 °C, 500 °C and 700 °C. The experimental results show that the microspheres have large response, fast response/recovery rate and good stability. The detection limits toward CO and C 2H 5OH of the microspheres annealed at 700 °C are below 1 ppm and 100 ppb, respectively. There is no obvious change in resistance and response within 1 month.