Abstract: Steel slag powder (SSP) is obtained by grinding steel slag, leveraging its high - alkalinity characteristic. SSP, as a low-cost alkali source, is used to activate peroxymonosulfate (PMS) for the degradation of tetracycline hydrochloride (TC). In the SSP/PMS system, the removal rate of 50 mg/L TC reaches up to 93.64%, and over 80% of TC can still be degraded after four consecutive cycles. Inorganic anions and humic acid have little impact on the system's performance. The SSP/PMS system not only shows excellent removal efficiency for TC but also has good removal effects on common organic dyes such as methylene blue and Congo red. Free - radical quenching experiments and electron paramagnetic resonance (EPR) analysis indicate that the main reactive oxygen species generated in the system were superoxide radicals (·O₂^-) and singlet oxygen (¹O₂). The degradation pathways of TC mainly involve demethylation, dehydroxylation, hydroxylation, and deamidation. The research offers a new approach for the efficient utilization of steel slag and the treatment of antibiotic wastewater.