Low weight loss NdFeB magnets are widely used in motors, wind power generators, variable frequency motors for air condition, pumps, sensors etc. The weigh loss of non coating magnet under the condition of high temperature, high pressure and high humidity can qualitatively reflects the working life of the magnet. Based on IEC68-2-66 test standard (Under 130 degree celscius, 100%RH, 2.7 bars), our weight loss is less than 5mg/cm2 after 20 days HAST test