Abstract: NdFeB magnet is the third generation permanent magnet for its high performance, anti-brittleness and low price. However, the inherent defect of NdFeB materials hampers its extensive applications to space electromechanical products. In this paper, as NdFeB magnet's two major defects, the thermal stability and the chemical stability are analyzed and measures are taken to solve the problem for applications in permanent magnet brushless DC motors, especially for applications in space.