We used Raman spectroscopy to systematically and comprehensively measure the concentrations of the main ion components (NH2COO-, HCO3-, and CO32-) in the CO2-NH3-H2O system for an initial total ammonia concentration [A] = 0.69, 0.88, 1.09, 1.34, 1.60, and 2.10 mol.L-1 and CO2 loading [C]/[A] = 0.18, 0.35, 0.43, 0.50, and 0.67, respectively. The experimental data were processed using two existing theoretical methods, and the analysis on results allowed us to propose a number of improvements based on these theoretical methods. Experimental results show that upon increasing [C]/ [A], the ratios of [NH2COO-] and [CO32-] to total carbon decrease linearly, whereas the ratio of [HCO3-] to total carbon increases linearly. The reaction process can be divided into three steps. Considering the impacts of experiment errors, [A] has little effect on the relative composition of the system in the range we studied. Results calculated with a revised theoretical method are in better agreement with the experimental data.