The origin of low coercivity of high La-Ce-containing Nd-Fe-B sintered magnets was analyzed based on characterization of the microstructure,magnetic domain structure,and magnetization reversal process.It can be found that the coercivity of magnet decreases sharply and the ratio value of coercivity(Hcj)to anisotropic field(HA)is below the theoretical value when the amount of La-Ce substitution for Nd is more than 40 wt％.The grain boundaries with poor magnetic isolation in the high La-Ce-containing Nd-Fe-B sintered magnets play an important role in reducing the coercivity of the magnet.In addition,a larger proportion of the reversible portions can be found for the magnet with a large content of La-Ce,which will lead to the low performance of the magnet.