The invention discloses a sintered Nd-Fe-B 
magnet with high 
corrosion resistance and the 
grain boundary reconstruction and a preparation method thereof. The composition of the invention is that: NdeFe100-e-f-gBfMg, wherein, e is greater than or equal to 6 and equal to or less than 24, f is greater than or equal to 5. 6 and equal to or less than 7, g is greater than or equal to 0.03 and equal to or less than 8, M is one or some of elements Dy, Tb, Pr, Sm, Yb, La, Co, Ni, Cr, Nb, Ta, Zr, Si, Ti, Mo, W, V, Ca, Mg, Cu, Al, Zn, Ga, Bi, Sn and In; The method is that: main 
phrase alloy and reconstructed 
grain boundary phase 
alloy are respectively pulverized and mixed uniformly; the 
powder mixture is pressed to a mould in the 
magnetic field, and fabricated into a 
sintering magnet in a high 
vacuum sintering furnace. By the reconstruction of the 
grain boundary phase composition, the invention can obtain the grain boundary phase 
alloy with 
low melting point and high 
electrode potential, decrease the 
potential difference between the main phase and the grain boundary phase on the basis of ensuring the magnetic properties, promote the intrinsic 
corrosion resistance of 
magnet, and has the advantages of simple process, low cost and being suitable for the 
batch production. Therefore, by combining the grain boundary reconstruction and double alloy method, the sintered Nd-Fe-B magnet with high intrinsic 
corrosion resistance can be prepared.