Asimple spectrophotometric flow-injection method is reported for the highly sensitive and fast determina- tion of iron(III) and total iron. The method is based on the formation of iron(III)- (1-nitroso-2-naphthol-3,6 sulphonate) (NRS) complex. The optimum conditions for the reaction of iron(III) with NRS is studied. And the complex is selectively monitored at λmax370 nm. With the reagent carrier solvent used was 5x10-4 M 1-nitroso-2-naphthol-3,6 sulphonate in 0.1 M acetic acid-acetate buffer solution at pH 4.0. Parameters affect simultaneously for the determination of iron(III) and interfering ions were tested. Relative standard deviation for five consecutive injections of 70 μg.L-1 iron(III) was 1.46% and for 5 μg.L-1 iron(III), it was 3.12%. The calibration graphwaslinearintheiron(III)concentrationrange0.1-100μg.L-1 andthelimitofdetectionwas0.05μg.L-1 for a 20 μL injection volume. The precision and accuracy of the method were checked by analysis of certified reference material and AAS method. The method was successfully applied to determine trace amounts of iron(III) and total iron in river and sea water samples.