Abstract: The results of EHMOcalculation indicated that the μ⁷(η², ω₂, ω₂') symmetrical double-end-on plus multiple-side-on flat-lying mode appeared to be more favorable to the coordination activation and hydrogenation of chemisorbed N₂ on iron catalysts for ammonia synthesis than other modes, and supported the associative reaction mechanism suggested by professor,K.R. Tsai.