To explore the degradation mechanism of trichloroethylene (TCE) in soil with persulfate (PS) activated by sulfated nano-zero-valent iron (S-nZVI), S-nZVI was prepared by the “one-step method”. A systematic investigation was carried out through batch processing tests combined with various characterization methods, chemical probe tests, and electron paramagnetization tests (EPR). The results showed that under the conditions of an initial PS concentration of 50 mmol/L, pH=3, Fe/S=10, and an S-nZVI dosage of 10 mg/g, the degradation rate of TCE in soil exceeded 85%. The EPR test results indicated that there were two types of free radicals, SO₄^·- and ·OH, in the system, and SO₄^·- was the dominant active free radical in the reaction. The GC-MS was used to infer that the degradation pathway of TCE was through the electrophilic addition of SO₄^·-, followed by the gradual dechlorination of intermediate products such as cis-1,2-dichloroethylene, vinyl chloride, and chloroethane, and finally degraded into ethane. This study demonstrated that the S-nZVI/PS system, as a new and efficient soil remediation technology, has broad application prospects in treating TCE pollution, providing theoretical basis and technical support for further optimizing the remediation schemes of sites contaminated by malodorous pollutants in the future.