A benzoxazine grafted poly(gamma-glutamic acid) (B-PGA) was successfully synthesized by esterification of poly (gamma-glutamic acid) (gamma-PGA) with benzoxazine (BX). Structural characterizations by FTIR, H-1-NMR, GPC and UV-Vis spectroscopy indicated that all of gamma-PGA monomer units were not grafted by BX thoroughly, and the reaction time of 2 h was the optimum condition for obtaining the B-PGA product with 25% degree of conversion. After modification, the maximum absorption wavelengths (lambda(max)) of gamma-PGA was shifted from 260 to 272 nm due to the aromatic pi ->pi* transition of BX in the B-PGA structure. For fluorescent properties, characteristic emission and excitation wavelengths of B-PGA including its fluorescence quantum yield were systematically analyzed. The results showed that the B-PGA exhibited strong fluorescence in bright green color by the influence of BX which functioned as a fluorophore. In addition, the B-PGA showed an interesting property of chemical sensing for Fe(III) ion which can be clearly observed by naked eyes from the changing of its photophysical properties such as color or fluorescence.