A sensitive and selective determination method of Fe(Ⅱ) ion by luminol-H2O2 system using a chelating reagent has been presented. A metal ion-chelating ligand complex such as Fe(Ⅱ)-diethylenetriamine pentaacetic acid (DTPA) produced higher chemiluminescence (CL) intensity as well as longer lifetime in luminol-H2O2 system than metal exist as free ions. Furthermore, the catalytic activity of Cu(Ⅱ) and Pb (Ⅱ) complexes with chelating reagents in luminol-H2O2 system was lost since chelating reagents act as a masking agent although free Cu(Ⅱ) and Pb(Ⅱ) ions have high catalytic activity. On the optimized conditions, the calibration curve of Fe(Ⅱ) ion was linear over the range from 1.0×10^(-7) to 2.0ⅹ10^(-5) M with correlation coefficient of 0.996. The detection limit was calculated to be 4.0×10^(-8) M.