A new degradation method for crystal violet (CV) from wastewater was proposed without adding any oxidant. The microwave catalyst of MgFe2O4-Fe2O3 was obtained through co-precipitation crystallization method, and its degradation performance for the wastewater containing CV was systematically evaluated under microwave irradiation, including catalyst dosage, microwave power and irradiation time. The results indicated that microwave catalyst MgFe2O4-Fe2O3 displayes excellent catalytic activity, and degradation efficiency for CV from a 200 mg/L wastewater can be highly up to 99.3% with microwave power of 800 W, catalyst dosage of 1 g/L, and irradiation time of 5 min. In addition, the mechanism for the microwave catalytic oxidation degradation was preliminary discussed, and hydroxyl radical (·OH) generated during the catalytic reaction acted as the dominant oxidant for the degradation, demonstrating from the experiment of adding different oxides as removal agents. Under microwave irradiation, microwave catalyst can effectively absorb electromagnetic wave to produce photo-electric effects with generation of electron-hole pairs (e-cb+h+vb), which will react with H2O molecules to produce ·OH, and then the formed ·OH groups oxidation can degrade the organic compounds existing in wastewater. The proposed microwave catalytic oxidation degradation is a new method for highly efficient degradation of organic wastewater.