The invention provides a process for treating waste denitration catalysts and relates to the field of waste recovery during coal combustion. A traditional way is broken through, the fact that all metal oxides can react with chlorine at the certain temperature and the feature that the melting point of the chlorine is much less than that of the oxides is utilized; under high temperature, the chlorine is fed into a boiling chloridizing furnace, and the metal oxides in all the waste denitration catalysts and silicon dioxide react with the chlorine within 1300 degrees. The chlorine exists in the form of gas and is mixed together, the feature that sublimation points of the different chlorine are different is utilized, the chlorine gas can be directly turned into solids in different temperature intervals, and solid density much higher than that of the gas can be crystallized and precipitated.