The perovskite catalyst La_0.9Sr_0.1Mn_0.03Pd_0.97O₃ doped with noble metal Pd was prepared by citrate method. The effects of noble metal Pd dopant on the morphology structure of perovskite and the NO_{x conversion, and the mechanism of SO2 on the NOx removal performance of La0.9Sr0.1Mn0.97Pd0.03O3 catalyst was investigated in this paper using X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and the transient response method. Results show that incorporating the noble metal Pd into the catalyst increased the specific surface area of the original catalyst, created a suitable place for NO contact, and improved the NO conversion of the catalyst effectively. The catalyst La0.9Sr0.1Mn0.97Pd0.03O3 has a weak sulfate phase after reacting in an SO2 atmosphere, indicating that sulfur resulted in a certain degree deactivation to the catalyst. The conversion efficiency of NOx was maintained above 80% and the temperatures of soot combustion is 353℃ in the presence of a lower concentration of SO2. When the concentration of SO2 increased, the temperatures of soot combustion increased to 368℃ and the conversion efficiency of NOx was only at 67%.}