Display omitted •α-Fe2O3/x%SiO2 (x = 0, 10, 15, 20, 30) were synthesized for the first time by sol-gel method.•The α-Fe2O3/20 %SiO2 had a good sensing response to acetone at 290 °C.•The α-Fe2O3/20 %SiO2 nanocomposite showed good sensitive and selective detection of acetone.•The α-Fe2O3/20 %SiO2 nanocomposite showed gas sensor response about 34 times higher than that of pure α-Fe2O3. Herein, a novel gas-sensing nanocomposite of α-Fe2O3/x%SiO2 (x = 0, 10, 15, 20, 30) was synthesized for the first time by sol-gel. With an increase in SiO2 concentration to 30 %, the average crystallite size and pore-size distribution of samples exhibited a decreasing trend. The surface area also showed an increasing trend with the introduction of SiO2. Gas-sensing measurement results revealed that the α-Fe2O3/20 %SiO2 nanocomposite showed the highest response (Ra/Rg = 50.20) to 500 ppm acetone at its optimal operating temperature of 290 °C, which was about 34 times higher than that of the pure α-Fe2O3 gas sensor. The response/recovery time of the α-Fe2O3/20 %SiO2-based sensor to 500 ppm acetone was 14 s/7 s. The response/recovery time of α-Fe2O3 was 25 s/21 s. After SiO2 was modified, the response/recovery speed increased. The results demonstrated the potential of α-Fe2O3/20 %SiO2-based gas sensors for sensitive and selective detection of acetone.