In order to improve the magnetic properties and corrosion resistance of sintered Nd-Fe-B magnets, (PrNd)_15.5B₆Cu_0.1Fe_balMg(wt%, x=0.1-0.3)permanent magnet was sintered by binary alloy method with adding MgO/Mg nanopowders at grain boundary.The magnetic properties, microstructures and corrosion resistance of sintered Nd-Fe-B magnets with different amounts of MgO/Mg (mass ratio 1:2) nanopowders were studied by means of permanent magnet automatic measuring instrument, scanning electron microscopy, X-ray diffractometer and CHI660E electrochemical workstation. The results show that when the content of MgO/Mg nanopowders is 0.1wt%, the comprehensive magnetic properties of the magnet are the best. At this time, the coercivity of the magnet is 1183 kA/m, the remanence is 1.22T, and the maximum magnetic energy product is 288 kJ/m^₃. The Tafel curve shows that the corrosion potential increases from -1.093V to -0.929V and the corrosion current density decreases from 223.87μA/cm^₂ to 42.66μA/cm^₂ with the increase of MgO/Mg nanopowders content. The electrochemical impedance spectroscopy shows that the radius of the high frequency capacitive arc of the magnet with appropriate amount of MgO/Mg nanopowders is larger than that of the high frequency capacitive arc of the magnet is not added, increasing the charge transfer resistance.Therefore, the magnetic properties and corrosion resistance of sintered Nd-Fe-B magnets are improved by adding appropriate amount of MgO/Mg nanocomposite powder at grain boundaries.