Abstract: A type of sintered NdFeB permanent magnet named as SPS NdFeB magnet was prepared by spark plasma sintering（SPS）technique.To better understand the magnetic hardening mechanism of SPS NdFeB magnets,the processes of magnetization and demagnetization at the room temperature have been investigated by means of Vibrating Sample Magnetometer（VSM）.The results showed that the magnetization characters of sample under a lower extrinsic applied magnetic field of 800 kA·m^-1 were obviously different from that of processes applied a higher external field of 1760kA·m^-1,in which the former can be termed as nucleation-controlled mode while the latter as pinning-controlled one.Compared with the curves in the processes of magnetization and demagnetization,it could be found that the coercivity of sample equals its pinning field of magnetization process.