Water-soluble polyaniline (PANI), prepared by chemical-oxide and SmBaCuMO5+δ (M=Fe, Co, Ni)(SBCM) powders, prepared by sol-gel method were analyzed through Fourier transform infrared spectroscopy (FT-IR) spectra, X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) respectively, so as to investigate the gas sensitivities of PANI/SmBaCuFeO5+δ (SBCF) and its sensitivity to NH3 under room temperature. The results showed that all of SBCM powders were of double-perovskite structure and PANI was successfully obtained. Under the same condition, the gas sensor based on PANI/SmBaCuFeO5+δ (SBCF) material exhibited higher resistance sensitivity, better selectivity and shorter response-recovery time than others. The resistance sensitivities to NH3 increased with the increasing of atom radius of M in PANI/SBCM.