Abstract: A series of Ru based ammonia synthesis catalysts supported by ceria with different promoter precursors,such as KF、KNO₃、Ba(NO₃)₂、CsNO₃,were prepared.Not only studied the effect of single and double promoters for the catalytic activity but also studied the effect of promoters’ kinds and content.N₂ physisorption,CO chemisorption and X-ray diffraction were carried out to investigate the effect of promoter on surface area,pore size distribution and ruthenium dispersion of catalysts.It has been found that the effectiveness of F ion just like the role of alkaline or alkaline-earth-promoter for ammonia synthesis.For the single-promoted Ru/CeO₂ catalyst,cesium proved to be most effective in the studied four promoters.For the double-promoted one,the activity of the catalyst was affected remarkably by cesium and barium co-exists.Ammonia synthesis concentration of over 13.3% was obtained over Ba+Cs-Ru/CeO₂ catalyst under 400℃,10 MPa and 10 000 h^-1.The structure and the surface property of Ru/CeO₂ catalyst were changed when promoters added.But the real factor to improving catalytic activity is electronic effect rather than structural factors.