A novel naphthalimide derivatives N-hexyl-4-benzylamino-naphthalimide(HBN) was synthesized from 4-bromo-1,8-naphthalic anhydride, and the structure was characterized by NMR and MS. Spectral properties of HBN for recognition of Fe3+ were investigated by fluorescence spectrum. In a certain range of Fe3+ from 4×10-7 to 1×10-2 mol·L-1, the fluorescence intensity of HBN significantly reduced with increasing concentration of Fe3+ in ethanol/water(1∶1, volume ratio). The equation of linear regression was F0/F=623.253 2cFe3++0.964 2 (R2=0.996 3). Moreover, no obvious interference with the detection of the Fe3+ ion was observed in the presence of the common metal ions such as Ca2+, Na+, Cu2+, Zn2+, Pb2+, Co2+, Ni2+, Mn2+ and Fe2+, which indicated that HBN displayed excellent selectivity and high sensitivity for the detection of Fe3+.