The performance characteristics of isothermal fluidized bed syngas methanation for substitute natural gas are investigated over a self-made Ni-Mg/Al

2

O

3

catalyst. Via atmospheric methanation in a laboratory fluidized bed reactor it was clarified that the CO conversion varied in 5% when changing the space velocity in 40-120 L·g

-1

·h

-1

but the conversion increased obviously by raising the superficial gas velocity from 4 to 12.4 cm·s

-1

. The temperature at 823 K is suitable for syngas methanation while obvious deposition of uneasyoxidizing C

γ

occurs on the catalyst at temperatures around 873 K. From a kinetic aspect

the lowest reaction temperature is suggested to be 750 K when the space velocity is 60 L·g

-1

·h

-1

. Raising the H

2

/CO ratio of the syngas increased proportionally the CO conversion and CH

4

selectivity

showing that at enough highH

2

/CO ratios the active sites on the catalyst are sufficient for CO adsorption and in turn the reaction with H

2

for forming CH

4

. Introducing CO

2

into the syngas feed suppresses the water gas shift and Boudouard reactions and thus increased H

2

consumption. The ratio of CO

2

/CO in syngas should be better below 0.52 because varying the ratio from 0.52 to 0.92 resulted in negligible increases in the H

2

conversion and CH

4

selectivity but decreased the CH

4

yield. Introducing steam into the feed gas affected little the CO conversion but decreased the selectivity to CH

4

. The tested Ni-Mg/Al

2

O

3

catalyst manifested good stability in structure and activity even in syngas containing water vapor.