Rare-earth composite oxide DyFeO3 was synthesized by adopting sol-gel method in citrate which belongs to the structure of peroviskite. Structural characteristics characterized by XRD and TEM indicate that this material is nanosized. The crystal structure shows a certain amount of lattice distortion due to the decrease of the grain size and the increase of the surface area. This material was made into gas sensors and measured its gas-sensing properties to ethanol, CO, H2, H2S etc. The results show that the sensors based on DyFeO3 have high sensitivity ,excellent selectivity and quick response&recovery behavior to H2S.