Abstract: To investigate the induced resistance and underlying physiological mechanisms of sulfur dioxide derivatives (SD) against tobacco black shank, this study evaluated the alleviating effects of root pretreatment with different concentrations of sulfites on Phytophthora nicotianae infection in tobacco line YM2020. The results showed that pretreatment with 1.0 mmol/L SD significantly reduced the disease index (by 56.1%) and relative electrical conductivity (by 53.4%) at 7 days post-inoculation, effectively alleviating disease symptoms. SD pretreatment significantly inhibited oxidative damage induced by pathogen infection. Compared with the inoculated control (CK+Pn), malondialdehyde (MDA) content in roots and leaves of the SD pretreatment plus inoculation group (SD+Pn) decreased by 18.1% and 17.4%, respectively, and reactive oxygen species (H₂O₂ and O₂^-) accumulation was also significantly suppressed, with reductions of 23.6% and 41.3% in roots, and 17.5% and 17.7% in leaves, respectively. Meanwhile, SD pretreatment significantly enhanced antioxidant enzyme activities: superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activities in roots and leaves of the SD+Pn group increased by an average of 27.1%, 42.3%, and 25.1%, respectively, compared with the CK+Pn group. Furthermore, SD treatment elevated glutathione (GSH) content and the GSH/GSSG ratio, and upregulated the activities and gene expression of defense-related enzymes, including phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO), β-1,3-glucanase (BGL), and chitinase (CHI). The transcript levels of key jasmonic acid (JA) signaling pathway genes, JAR1 and MYC2, were also significantly increased. In conclusion, SD may enhance systemic resistance in tobacco against black shank by strengthening the antioxidant defense system, maintaining redox homeostasis, and synergistically activating the JA signaling pathway and downstream defense gene expression.