Ferrous iron (Fe(II)) is essential to organisms, but ferric iron (Fe(III)) is toxic. Monitoring Fe(II) and Fe(III) in solution can improve our understanding of Fe biogeochemistry and toxicity. However, it is difficult to rapidly determine Fe in different valence states in solution using traditional methods. A novel method, laser-induced breakdown spectroscopy coupled with chelating resin selective enrichment by adjusting the solution pH, for determining Fe(II) and Fe(III) in solution is presented here. The sample solution flow rate and solution pHs were optimized to obtain a better enrichment effect. The calibration curve for Fe(II) and Fe(III) were established and the limits of detection were 0.120 mg L⁻¹ and 0.142 mg L⁻¹, respectively. Single valence state Fe in an Fe(II) and Fe(III) mixed solution was separated based on the enrichment abilities of Fe(II) and Fe(III) at different pH values of the chelating resin, and the separation relative error ranges were 0.25%–1.12% and 3.05%–7.24%, respectively. The recoveries of Fe(II) and Fe(III) in real spring water were 100.62% and 99.11%, respectively. The results indicated that the method of LIBS coupled with chelating resin selective enrichment can rapidly and accurately quantify Fe in different valence states in aqueous solution.