CO adsorbed infrared spectroscopy study was conducted in this work in order to better understand the significantly improved anti-coke performance of Ni/Al2O3 catalyst obtained via argon glow discharge plasma treatment. The present study revealed a significant decrease of linear to bridge (L/B) adsorbed CO for glow discharge plasma treated Ni/Al2O3, compared to that for untreated Ni/Al2O3, indicating an enhancement of close packed plane concentration. This structure change leads to lower methane turnover frequency (TOF) and better balance of carbon formation-gasification, resulting in better anti-coke property of Ni/Al2O3 for CO2 reforming of methane.