Morphology, size and changes in the Fe NPs surface were characterized using SEM, XRD, and FTIR techniques, showing that Fe2O3 and Fe3O4 was formed and green tea extract contained a high concentration of caffeine/polyphenols. It acted as both reducing and capping agents in the synthesis of Fe NPs. To further confirm the removal mechanism of MG by the functional Fe NPs, the degraded products were identified by FTIR and GC–MS analysis. Finally the mechanism of Fenton-like oxidation of MG based on both adsorption and degradation was proposed.