Syngas production via dry reforming of methane (DRM) was experimentally investigated using Ni-based catalyst. Ni/Al2O3 modification with CeO2 addition and O2 addition in the reactant were employed in this study to suppress carbon deposition and to enhance catalyst activity. It was found that DRM performance can be enhanced using CeO2 modified Ni/Al2O3 catalyst due to CeAlO3 formation. However, an optimum amount of CeO2 loading exists to obtain the best DRM performance due to the decrease in specific surface area as the CeO2 loading increases. Without O2 addition, the reverse water-gas shift reaction plays an important role in DRM. It was found that CH4 conversion and CO yield were enhanced while CO2 conversion and H2 yield are decreased as the CO2 amount in feedstock increased in DRM. With O2 addition in the fed reactant, it was found that the methane oxidation reaction plays an important role in DRM. CH4 conversion can be enhanced by O2 addition. However, decreases in CO2 conversion and H2 and CO yields occurred due to greater H2O and CO2 productions from the methane oxidation reaction. The thermogravimetric analysis (TGA) results showed that CeO2 modified Ni/Al2O3 catalyst would have the lowest amount of carbon deposition when O2 is introduced into the reaction. •Syngas production via dry reforming of methane (DRM) was experimentally studied.•CeO2 modification on Ni/Al2O3 catalyst was used to suppress the carbon deposition.•O2 addition in the reactant was used to suppress the carbon deposition.•DRM performance depends on the CeO2 loading in the Ni/Al2O3 catalyst.•Methane oxidation is the key reaction in DRM with O2 addition.