Abstract: The ruthenium catalyst supported on activated carbon was prepared by the impregnation method. The effect of such factors as dryness, pH value during precipitation, surface area and porosity of the activated carbons, sequence of precipitation, etc on the catalytic activity and Ru dispersion were studied during preparation. The results showed that activated carbon should be dried at 100—200 ℃ for 6—8 h before precipitation. Also, activated carbon must have enough surface area, especially the developed mesopores, which provided enough sites for Ru deposition. It was also found that the surface area and porosity of activated carbon changed greatly during precipitation. Barium promoters might provide the deposition surface for Ru, while potassium might fill in mesopore and contact with Ru, providing electrons for Ru. In order to obtain good Ru dispersion, the pH of the aqueous solution of RuCl₃•3H₂O should be controlled at 0.40—1.05, and the sequence of precipitation should be Ba-Ru-K. Only then could good performance of Ru-based ammonia synthesis catalysts be achieved.