Ordered mesoporous Zr-doped In₂O₃and undoped In₂O₃nanostructures were synthesized via nanocasting method which is an easy, repeatable and friendly route. Zr incorporation might lead to In₂O₃lattice deformation without destroying the original crystal structure and increased chemical adsorbed oxygen species. Gas sensors based on undoped and Zr-doped In₂O₃were fabricated and their NO₂gas sensing properties were tested. The sensor performance was improved by Zr-doped strategy. The Zr-doped In₂O₃based sensor showed good response (169) toward 1 ppm NO₂at the operating temperature of 75℃with low resistance of 23 k Omega and the detection limit was 20 ppb. Such favorable sensing performances endowed mesoporous Zr-doped In₂O₃with a potential application in the field of gas sensor. The enhanced sensing properties were mainly attributed to its mesoporous microstructures, increased chemical adsorbed oxygen and limited grain size by Zr-doping.