The geometries, electronic, and growth strategies of the cation clusters have been investigated using all-electron density functional theory. The results show that H is transferred from NH (n) to Fe (m) when hydrogen supersaturated or the cluster size of Fe (m) is larger. clusters are more stable than other considered clusters by the second derivative of the binding energies. From the highest occupied molecular orbital-lowest unoccupied molecular orbital gap curves, it can be seen that the Fe4NH+; have higher chemical reactivity. Summarizing up the association energies of Fe (m) NH+, it can be seen that -NH, Fe-4-NH+, and Fe-3 + are the main three channels to product Fe4NH+.