The microstructure, surface morphology, and magnetic properties of the sintered NdFeB permanent magnet prepared by the HDDR method were analyzed by X-ray diffraction, scanning electron microscopy and BH magnetic measurement. Microstructural studies show that NdFeB magnets which were firstly prepared by HDDR powder and then sintered at the high-temperature of 1080 oC consist of a large amount of the tetragonal phase Nd2Fe14B (P42/mnm) and trace amount of rare earth-rich phase. SEM images indicate that the average grain size of the Nd2Fe14B phase is about 12.3 μm. The density factor of (006) crystal face of Nd2Fe14B phase is estimated as about 3.5 using Horta formula, suggesting that the sample has a strong c-axis orientation. The demagnetic curves at different temperatures show that at room temperature this sample has well magnetic properties, i.e. (BH)max 264 kJ/m3, remanence Br about 1.17 T, and coercive Hcj 2038 kA/m. With the temperature increasing, magnetic properties of the samples are monotonicly reduced, especially for the coercivity which is reduced by 1496 kA/m from 295 to 448 K. The coercivity mechanism of the NdFeB magnets prepared by HDDR method was analyzed by studying the behavior of Hc(T)/Ms(T) versus (T)/Ms(T) (Kronmüller-plot). The results of Kronmüller-plot show that nucleation is the dominating mechanism for the magnetization reversal in these samples. Micromagnetic parameters αk of 1.39 and Neff of 1.75 are responsible for the high coercivity of magnetic alloys.