Abstract: The HDDR (Hydrogenation-disproportionation-desorption-recombination) is a special process to produce Nd2Fe14B -based permanent magnet powder. The effects of HD and/or DR temperature on the properties of high performance Nd-Fe-B magnet powders produced by HDDR process were investigated, with X-ray diffraction (XRD) used to analyze the phase component of the alloy in various treating conditions. The results show that the magnetic properties of the Nd-Fe-B powders are sensitive to either HD or DR temperature and adding the alloying elements Ga and Al into them can improve their magnetic properties. Although the remanence of magnetic powders will be improved by way of eliminating the harmful α-Fe phase, the phase can not be eliminated completely by homogenizing treatment. The major phase Nd2Fe14B is decomposed into three phases, i.e., α-Fe, NdH2 and Fe2B, during HD stage, then the major α-phase grain size becomes finer after DR stage, about 0.28 μm as calculated.