Hybrid Au@_In2O3microstructures with a distinctive core-shell configuration have been successfully synthesized by employing Au@ carbon spheres as sacrificial templates. The In₂O₃shell can be easily decorated on the Au core by a facile aging process at room temperature ( 25℃) combined with a subsequent calcination. Field emission electron microscopy and transmission electron microscopy images revealed that the Au@ In₂O₃core-shell structures had an average diameter of about 150 nm and the thickness of the porous In₂O₃shell was ca. 50 nm. When tested as a potential sensing material for gas sensing, the resulting hybrid Au@ In₂O₃core-shell structures exhibited a higher response to formaldehyde compared with the pure In₂O₃spheres. The enhanced sensing properties of Au@ In₂O₃core-shell structures were attributed to their intense electron depletion that arose from the catalytic activity of Au nanoparticles and the formation of metal-semiconductor.