The invention relates to dye wastewater disposal, in particular to a method for preparing a catalyst for disposing the combined modification of dye wastewater. The method specifically comprises the following steps: 80 to 200 ml of hydrazine hydrate is added into 150 to 400 ml of a copper sulfate pentahydrate solution in a stirring state, is aged for 15 to 35 minutes, is subsequently added with 15to 30 grams of industrial iron powder, is stirred for 2 to 5 minutes and is filtered to obtain sediment; and the sediment is washed through distilled water and is dried to obtain the catalyst. The method effectively combines two methods of internal electrolysis and photocatalysis together to prepare the high-efficient, economic and innoxious catalyst and has the advantages of stable performance, high efficiency, wide applicability, no pollution, friendliness to environment, thereby strengthening the dye wastewater disposal. The catalyst has a simple preparation process, mild reaction condition, and cheapness and wide source of raw materials.