The N-2 plasma treated Ni/Al2O3 catalyst was enhanced by manganese (Mn) promoter with doping content ranging from 5 wt% to 15 wt%. Compared to the plasma treated nickel catalyst without Mn additive, the introduction of Mn promoter further increased the CH4 conversion of studied catalysts about 10% at 700 degrees C for CO2 reforming of methane. After 360 min reaction of time-on-stream, the deactivation degree value was decreased to 1.46%. Relatively lower value of 5-10 wt% doping amount of Mn was appropriate. Mn promoter further intensified the reducibility of plasma treated catalyst according to the shift to lower temperature of the reduction peak shown in H-2-TPR profiles. CO2-TPD results suggested that the modification effect of Mn promoter on the basicity of plasma treated catalyst was speculated to account for the concentration increase of absorbed CO2. It was beneficial to the carbon deposition elimination and it increased the coking-resistant ability of catalyst surface, while this result was in good agreement with the CO2-TPSR and TG results. The lower temperature and smaller area of CO peak was observed over plasma treated Ni-Mn/Al2O3 catalyst in CO2-TPSR test, i.e., less coke formation on the Mn promoted sample. (C) 2015 Elsevier B.V. All rights reserved.