A novel ammonia synthesis catalyst, alkali-promoted ruthenium supported on multi-walled nanotubes (MWNT), has been developed. Various alkali-promoters and carbon-based supports were compared. The effects of the contents of Ru and K, the treatment of MWNT, and the reaction temperature on ammonia synthesis activity were investigated. It was found that, as a support, the MWNT is much better than other carbon-based supports. The yield Of NH3 was 47.423 ml NH3/h g-cat at 693 K, at atmospheric pressure and N-2/3H(2) flow-rate of 1800 ml/h for the catalyst with K/Ru/MWNT = 4/4/100 (w/w).