In this study, a series of SiO₂@ZrO₂-supported catalysts was employed for the methanation of CO/CO₂ in a fixed-bed reactor to address the issues of insufficient low-temperature activity and sulfur poisoning of catalysts during CO/CO₂ methanation. Mesoporous SiO₂@ZrO₂ core–shell supports were prepared via the sol-gel method and liquid-phase coating process, and Ni-CeO₂-ZnO catalysts supported on SiO₂@ZrO₂ were synthesized by incipient wetness impregnation with Ni as the active component and CeO₂-ZnO as promoters. Catalysts with optimal methanation performance and sulfur resistance were screened by regulating the ZrO₂ shell loading (7%, 15%, 23%), Ni loading (5%, 10%, 15%, 20%), and Ce/Zn promoter molar ratio (3:1, 1:1, 1:3). The structural properties and catalytic mechanism were analyzed using multiple characterization techniques, including XRD, SEM, TEM, XPS, and H2-TPR. The results showed that: (1) the Ni-CeO₂-ZnO/SiO₂@ZrO₂ catalyst achieved CO and CO₂ conversions of 92.37% and 87.63%, respectively, with CH4 selectivity exceeding 99%; after exposure to 50 ppm H₂S, the catalyst retained 85% of its initial activity in a 500 h stability test. (2) Characterization revealed that the mesoporous SiO₂@ZrO₂ support suppressed Ni sintering and accelerated mass transfer; ZnO preferentially adsorbed H₂S to form ZnS, protecting the Ni active sites, thereby enabling efficient CO/CO₂ methanation and sulfur resistance of the catalyst.