Abstract: Through microwave magnetizing roasting the Jiugang’s specularite in the high temperature microwave reactor,the heating characteristic of specularite under microwave treatment,phase transformation before and after magnetic roasting and the effect of microwave heating on the microstructure were investigated. It was shown that the mineral absorbed microwave power effectively and could be heated up to more than 500 ℃ in 15 minutes by microwave heating. SEM analysis indicated that intergranular fractures occurred both in the conventional heated sample and microwave heated sample,but the form of crack was different. The crack in the sample by conventional magnetizing roasted was mainly caused by siderite decomposition,but the crack in the sample by microwave heated widely distributed in the siderite and also the specularite and the interface between specularite and gangues. These crack are expected being caused by excess internal stress due to the selective microwave heating result.