The synergetic effect of commercial catalyst Ni/Al2O3 with the low-temperature plasma created by a dielectric barrier discharge (DBD) for the dry reforming of methane was investigated in a coaxial DBD reactor. Three different contact modes of prereduced catalyst with plasma were studied to determine the interaction of plasma and catalyst, especially their synergetic effect. When the catalyst was placed at the end of the discharge zone or absolutely separated with the discharge zone, there was no synergetic effect or much worse effect than only using plasma or only using catalyst. However, when the catalyst was fully filled in the annular discharge gap, the synergetic effect was achieved. In addition, with the increase of temperature, the synergetic effect appeared to be evident from 673 K. The experiments also demonstrated that the unreduced catalyst filled in the annular discharge gap can be in-situ reduced during the reaction at around 673 K by the assistance of the in-situ plasma. However, the synerget...