A new chemiluminescence (CL) reagent named 4-amino-5-thiocyanato-phthalyl-hydrazine (iso-luminol-SCN) is synthesized by the bromide-mediated substitution reaction of iso-luminol with sodium thiocyanate in dimethyl formamide (DMF) at room temperature.Strong CL is observed for iso-luminol-SCN oxidized by hydrogen peroxide (H2O2) in the presence of Fe2+,with the CL intensity strongly depending on the concentration of Fe2+ and being hardly interferred by other common metal ions.Based on this fact,a flow injection CL method is established for the high sensitive and selective determination of Fe2+.The CL intensity was linearly correlated with the concentration of Fe2+ in the range of 1.0 × 10-8 mol·L-1 to 1.0 × 10-5 mol·L-1 following the equation CLnet =166.3c + 57.7 (c,×10-6 mol·L-1;n =7;R2 =0.9988).The detection limit is calculated to be 3.2 × 10-9 mol·L-1 Fe2+ based on the 3S0/K principle.The relative standard deviation (RSD) was 3.7％ for 1.0 × 10-6 mol·L-1 Fe2+ (n =11),a support for the precision of Fe2+ measurement.The recover-ies of Fe2+ were obtained in the range of 98.8％-101.6％ in three real water samples,showing the applicability and reliability by the proposed method.The possible CL mechanism is proposed based on the kinetic characteristic of the CL reaction and the CL spectrum.