Abstract: In this paper, non-equilibrium plasma discharge technology and Ce-Mn catalytic method are used to promote low temperature and high efficiency conversion of thin methane in the fireflood exhaust. The conversion performance of thin methane under catalyst, plasma and their coupled synergistic effect were compared and analyzed. The effects of CH₄/O₂ molar ratio (0.1~0.5), heating temperature (250~375℃) and plasma discharge power (9~21 W) on methane conversion were investigated. The results show that the synergistic effect of plasma discharge and Ce-Mn catalyst is significant, and the methane conversion rate is as high as 62.93% at 375℃ and 21 W, which is about 50% and 60% higher than that of plasma only and catalyst only, respectively. Under the synergistic effect of plasma discharge and Ce-Mn catalyst, the methane conversion rate increases with the increase of heating temperature. When the heating temperature rises from 325℃ to 375℃, the average methane conversion rate increases by about 20.7%. The methane conversion rate increases linearly with the increase of plasma discharge power, and the average rate is about 2.46%/W. The methane conversion rate is inversely proportional to the methane/oxygen molar ratio. When the methane/oxygen molar drops from 0.5 to 0.1, the methane conversion rate increases by about 29.46%.