The conformational transition of poly γ-glutamic acid (γ-PGA) embedded with magnetite nanoparticles under various pH conditions was investigated by Fourier transform infrared spectroscopy (FTIR). The secondary structure content was determined through the analysis of amide Ⅰ bands of Fourier deconvolution spectra, secondary derivative spectra and the Gaussian curve fitting of the original infrared spectra. The results showed that the conformation of the γ-PGA was affected by solution pH. The total contents of β-sheet and β-turn were higher than 65％, while α-helix and random coil were low. The content of β-turn increased with increasing pH, while the β-sheet decreased. Additionally, the zeta potential results showed that the pH-sensitive secondary structure of γ-PGA had influence on the stability of suspension of magnetic γ-PGA nanospheres. The minimum value of zeta potential (-35.4 mV) was obtained at pH 10.2.