Based on the method of quantitative pyrolysis of ammonium sulfate, sulfur tolerance of Pd/beta zeolite in catalytic conversion of toluene was explored in this paper. Changes in pore structure, valence, acidity, oxidation, and adsorption/desorption behavior were investigated in detail through XRD, N₂ adsorption, HRTEM-EDS, XPS, H₂-TPR, and NH₃-TPD before and after sulfur poisoning. The results proved the structural stability of Pd/beta zeolite in the process of sulfur poisoning. Combined with FT-IR and ICP characterization results, the possible sulfur poisoning process and the intrinsic sulfur tolerance mechanism of Pd/beta zeolite were revealed: Active PdO/Pd reacted with sulfur species to produce inactive PdSO₄ was regarded as a major cause of partial deactivation of Pd/beta zeolite. AlO₄ units in beta zeolite were likely to combine with sulfur species to obtain Al₂(SO₄)₃ and generate more acidic sites, and SiO₄ units in beta zeolite were structurally stable enough to resist sulfur corrosion, guaranteeing the stability of the catalyst. The catalyst catalytic performance was not seriously affected after deep sulfur poisoning, exhibiting good resistance to sulfur poisoning.