Abstract: The ammonium ions produced by the reactions of relatively excessive dimethylhydroxylamine(DMHAN) with Fe³⁺, Ce⁴⁺ and Pu⁴⁺ in dilute nitric acid solutions at room temperature were determined by ion chromatographic method. The results show that the reactions between DMHAN and Fe³⁺, Ce⁴⁺ and Pu⁴⁺ all produce a certain amount of ammonium ramifications under acidic conditions, which includes (CH₃)₂NH⁺₂, NH⁺₄ and CH₃NH⁺₃. The reaction mechanism is as follows. When DMHAN reacts with Fe³⁺, Ce⁴⁺ and Pu⁴⁺ respectively, it can be oxidized and reduced simultaneously in the acidic solution for the  -1 valence of N atom in DMHAN. Then part of DMHAN is reduced to (CH₃)₂NH⁺₂, and it is further converted into NH⁺₄ and CH₃NH⁺₃ partly. With the increase of redox potential of Fe³⁺, Pu⁴⁺ and Ce⁴⁺, the conversion ratio of DMHAN into amine ions increases and the proportion of (CH₃)₂NH⁺₂ in total amine ions decreases, while the proportion of NH⁺₄ in total amine ions increases.