Abstract: This paper reports a new complex chemiluminescence,i.e.luminol-IO₄-catalyzed by Fe(1,10-phenanthroline)₃²⁺ complex. Based on this catalysis a new chemiluminescence method for the determination of trace Fe(Ⅱ) is proposed. The detection limit is 1.6×10^-7g/L Fe(Ⅱ),the linear dynamic range is 1×10^-5-1×10^-3g/L Fe(Ⅱ) and the variation coefficient at an iron concentration of 2×10^-4g/L Fe(Ⅱ) is 3.5% (n=10).This method has ho satisfactorily applied to the determination of trace iron ion in precipitated BaSO₄ samples.