[Objective] The influence of different metal ions on the growth and nitrogen removal ability were studied to identify the suitable metal ions and their concentrations for strain C16. [Methods] Mg2+, Mn2+, Fe2+, Cu2+ and Zn2+ ions were selected to study their influence on the growth, nitrogen removal ability, NO2?-N accumulation and activity of relative enzymes of strain C16. [Results] Mg2+ significantly promoted the growth and NH4+-N oxidation rate of strain C16; C16 could not grow in higher concentrations of Mn2+; lacking of Fe2+ in original medium inhibited the growth and NH4+-N oxidation rate of C16; adding 0.1 mmol/L Cu2+ in the original culture medium could stimulate the growth and nitrogen removal rate of strain C16, meanwhile NO2?-N and NH2OH were only present in trace amounts; the existing of Zn2+ of different concentrations inhibited the growth and NH4+-N oxidation rate of C16. A further enzyme testing results showed that, 0.1 mmol/L Mg2+ promoted the activity of hydroxylamine oxidase (HAO); 0.1 mmol/L Cu2+ promoted nitrate reductase (Nar) and nitrite reductase (Nir) activity. [Conclusion] Mg2+ was necessary for the growth and nitrogen removal of strain C16. The addition of Cu2+ could avoid excessive accumulation of nitrite.