Disclosed herein is a method for treating waste byproducts from terephthalic acid processes, by homogeneously mixing the waste byproducts with water and an anti- corrosion agent to prepare a waste water, decomposing organic compounds of the waste water through oxidation reaction with an oxidant under the condition that the waste water is kept in a liquid state, and recovering catalyst particles from the liquid component. The method is of high industrial applicability as it allows organics to be decomposed with the waste byproducts maintained in a liquid state and can recover catalysts with high yield availability.