Abstract: In this study, greenhouse gas and argon (CO₂/Ar) were used as carrier gas to produce gas-liquid plasma to treat tetracycline hydrochloride in water. The CO₂ decomposition of CO₂/Ar gas-liquid plasma, the production of reactive species (such as OH, ¹O₂, O, H₂O₂, O₃), and the degradation mechanism of tetracycline hydrochloride under different parameters were studied. In the gas phase, the effects of CO₂/Ar ratio and gas flow rate on CO₂ conversion were investigated. The effects of CO₂/Ar ratio, different initial concentrations, gas flow rate and initial pH on the degradation of tetracycline hydrochloride were investigated in the liquid phase. Combined with the spectral diagnosis, the characterization of liquid phase reactive species, and the relevant quenching agents, the production rules of different reactive species and their effects on the degradation of tetracycline hydrochloride were analyzed. Finally, the intermediate products produced in the degradation process were detected, and the degradation principle and possible degradation pathway of tetracycline hydrochloride in this system were proposed. It provides a new idea for CO₂ utilization and water pollution control.