With the increasingly application of SF6 in the power industry, the annual emissions have reached a considerable scale. Because of its high global warming potential (GWP) value, the harmless treatment of SF6 after degradation is important. In this paper, the SF6 with a concentration of 2% was degraded by a self-designed DBD plasma reactor under flowing conditions. The effects of adding H_2O and O_2 on the degradation efficiency and products of SF6 were analyzed. Studies show that when H_2O or O_2 is added alone or when both are added, the degradation rate of SF6 can be greatly increased, and the degradation rate of high concentration SF6 (2%) is increased from 60% to more than 96%; Under the addition of 0.5% H_2O and 2% O_2, the degradation rate of SF6 reaches 98.2% at a flow rate of 50 ml/min. The results of GC-MS and FTIR show that the participation of H_2O tends to generate SO_2 during the degradation of SF6, and the involvement of O_2 tends to generate SO_2F2, which provide a research direction for the regulation of degradation products.