Porous alpha-Fe2O3 nanoparticles were synthesized by simple annealing of beta-FeOOH precursor derived from a facile hydrothermal route, the structures and morphologies of the as-prepared product were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that the average crystallite size of the obtained porous alpha-Fe2O3 was 34 nm and exits numerous irregularly distributed pores with a diameter varying from 2 nm to 10 nm on the particle surface. The gas-sensing properties of the sensor based on porous alpha-Fe2O3 nanoparticles were investigated, and the result showed that the sensor exhibited a high performance in hydrogen sulfide (H2S) detection at room temperature. The highest sensitivity reached 38.4 for 100 ppm H2S, and the detection limit was as low as 50 ppb. In addition, the response of the sensor towards other gases including C2H5OH, CO, H-2 and NH3 indicates the sensor has an excellent selectivity to detection H2S gas. Finally, the sensing mechanism of the sensor towards H2S was also discussed. (C) 2015 Elsevier B.V. All rights reserved.