• The tannin acid reduced graphene oxide membranes exhibit good separation performance. • The rejection rate of Hg 2+ could be enhanced by tannin acid modification. • The membrane was suitable for reusing without reducing the performance. • The rGO-TA membrane shows excellent potential in desulfurization wastewater treatment. In this study, the tannic acid reduced graphene oxide (rGO-TA) membrane was prepared by vacuum-assisted filtration method. The as-prepared membrane was characterized by Transmission electron microscope (TEM), atomic force microscope (AFM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). It was found that the GO membrane was modified by the polyphenolic hydroxyl groups in the tannic acid (TA), and the membrane structure was getting more compact. Besides, the separation performance of the rGO-TA membrane was evaluated, and the separation mechanism had been further explored. The effect of reduction degree, rGO-TA loading, initial concentration of Hg 2+ , and temperature were studied. The results show that the separation performance was related to the reduction degree of the rGO-TA membrane, the optimum Hg 2+ rejection rate of 91.61%, and the flux of 56.5 L·m −2 ·h −1 could be achieved. The separation performance was strongly dependent on the rGO-TA loading. The higher initial concentration of Hg 2+ could adversely affect the separation performance. The given temperature would change the hydration degree of the groups in the membrane and increase the Hg 2+ rejection rate. Moreover, the rGO-TA membrane exhibited an excellent regeneration performance (rejection rate of 78.74%) after three cycles.