Abstract:The results of experiments of mixed field irradiation demonstrated that irradiation experiments had different effects on two kings of permanent magnet (45SH and 52N), of which magnet flux reduced accordingly. The magnetic flux decreased remarkably for N52 magnet, magnetic flux loss up to 6. 205%, while the flux loss of 45SH was 0. 205%. The permanent magnets were re- magnetized after irradiation, and the recovery rate of magnetic flux were all above 99. 8%. It meant that the crystalline structure of the permanent magnet was not transformed after the irradiation, which proved through XRD. The mechanism of irradiation demagnetization had something to do with the energy and dose of incident particles. When the dose of incident particles was lower, the mechanism of irradiation demagnetization was identical with thermal demagnetization.