Abstract: Sintered Nd-Fe-B, Nd-Fe-B-Sn and Nd-Dy-Fe-B-Sn permanent materials were prepared through powder metallurgy technology.Their microstructure have been investigated with SEM,EPMA and TEM. In addition,their magnetic properties were characterized by means of magnetometer and VSM at room and elevated temperature. It is showed that, in microstructure, phases of alloy added tin remains Φ,Nd-rich and η.None of other phase has been found,but tin atom solves in Nd-rich phase.This results in the improvement of wettability betweenΦ grains and Nd-rich.The magnetic properties of Nd-Fe-B are degraded at room temperature because of adding tin.However, the thermostability of magnetic properties is increased at elevated temperature, Lirr and β Hc reduced remarkably,when tin has been introduced into alloy’s constituent.So,the improvement of magnetic properties should correlate with the change of microstructure benefited from adding tin.