Sensing properties of $alpha$-Fe2O3 thin film to reducing gases such as CHx and CO were systematically examined after deposition on Al2O3 substrate by PECVD(Plasma Enhanced Chemical Vapor Deposition)technique. Microstructure of deposited $alpha$-Fe2O3 thin film showed the porous island structure. This specimen was annealed at 450, 550, $650^{circ}C$ to enhance the gas sensing properties and investigated in terms of CO and C4H10 concentration from 500ppm to 3,000 ppm at operating temperature of 35$0^{circ}C$ The gas sensitivity(%) to C4H10 measured at the operating temperature of 35$0^{circ}C$ was 98.24 (highest sensitivity) 69.51 to CO and 2% to CH4 respectviely.