Abstract: The plant polyphenol was modified by amine methylation, and then coated onto Fe₃O₄ surface to obtain the functional Fe₃O₄@amine-methylated plant polyphenol (Fe₃O₄@A-PP) for harvesting the oleagious microalgae-Chlorella vulgaris. FTIR, magnetic hysteresis loop, and zeta potential of Fe₃O₄@A-PP were detected to investigate its physicochemical properties. The effects of dosing mode of Fe₃O₄@A-PP and the ratio of Fe₃O₄ to A-PP on harvesting efficiency were also studied. FTIR indicates that Fe₃O₄@A-PP has the functional groups of C-H, N-H, and -OH from A-PP. The coating of A-PP onto the Fe₃O₄ surface don't interfere the magnetic property of Fe₃O₄. Compared with A-PP, the zeta potential of Fe₃O₄@A-PP is improved by 5-10 mV. The ratio of Fe₃O₄ (g/L) to A-PP (mg/L) in Fe₃O₄@A-PP influences the harvesting efficiency obviously and the highest efficiency of 84.2% is achieved at 20/200. Fe₃O₄@A-PP can shorten the harvesting time from 30 min of A-PP to less than 0.5 min. The microscope images show that the microalgae cells are wrapped by Fe₃O₄@A-PP and form the cluster matrix or adhere around the Fe₃O₄, unlike the flaky and loose flocs or aggregates after A-PP flocculation. The mechanism of charge neutralization in the Fe₃O₄@A-PP magnetic flocculation plays an important role in microalgal harvesting.