Variable frequency compressor motor permanent magnet material generally uses NdFeB,high temperature permanent magnet will produce demagnetization phenomenon,demagnetization will lead to motor overheating,winding burn,refrigeration oil deterioration,crankshaft wear and a series of problems.This paper mainly explores the mechanism of high temperature demagnetization of variable frequency air conditioning compressor,and studies the method of anti-high temperature demagnetization by key control factors to improve the reliability of compressor.