Abstract: Nano zero valent iron nanoparticles (GS-nZVI) were green-synthesized with pomegranate peel extract as the reducing agent and stabilizer. The physical and chemical properties of GS-nZVI product were characterized with scanning electron microscope (SEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscop (FTIR), X-ray photoelectron spectroscop (XPS) and Thermo-Gravimetric Analysis (TGA). The particle size and surface Zeta potential of the products were measured with the laser-scattering Zetasizer instrument. Based on the basic principle of chemical equilibrium, the effects of synthesis conditions such as reaction time, iron salt concentration and polyphenol concentration on the particle size and yield were discussed and the possible mechanism was proposed. The results showed that GS-nZVI synthesized from pomegranate peel extract had an amorphous structure and polyphenols in the extract not only reduced the ferritic salt (Fe²⁺) to Fe⁰ but also coated on the surface of nanoparticles as a stabilizer to improve the dispersion of the samples. The results proved that 120 min reaction time, 0.05 mol/L Fe²⁺ and 15 mg/mL polyphenol was the best preparation condition of GS-nZVI with the highest yield and the smallest particle size, and the mean particle size was 213 nm.