The invention discloses a mixed acid catalysis system for a ketoxime beckmann rearrangement reaction. The mixed acid catalysis system is characterized in that the catalysis system is a homogeneous system consisting of an organic acid and an inorganic acid, and serves as a catalyst in a reaction of preparing amide through ketoxime rearrangement; the reaction temperature is 60-130 DEG C, preferably 80-120 DEG C; the reaction time is 1-240min, preferably 20-90min; the molar ratio of the organic acid to the inorganic acid is 0.5-50, preferably 3-20; the molar ratio of the inorganic acid to the ketoxime is 0.1-10, preferably 1-5. According to the catalysis system, the ketoxime can be efficiently converted into a corresponding amide compound in a relatively mild reaction condition; moreover, the content of byproducts of the reaction can be controlled, and particularly, the content of heavy byproducts is very low. The organic acid part of the catalysis system can be recycled, and the reaction condition in use is mild; the conversion rate of the ketoxime rearrangement reaction is high, and the selectivity is good; the content of byproducts after the rearrangement reaction is low, and particularly, the content of heavy byproducts is very low in an optimized condition; the aftertreatment process is hopefully to be simplified; the catalysis system has a good potential in industrial application.