The invention relates to a catalyst for pyrolyzing coking wastewater by using converter high-temperature flue gas and an application method thereof, belonging to the technical field of ferrous metallurgy and chemistry. The chemical formula of the catalyst comprises the following materials in percentage by weight: 6.50-12.50% of titanium potassium oxalate, 4.80-10.00% of 18-niobium tungsten manganese phosphate, and the balance of water. After the materials are weighted according to determined formula contents, the titanium potassium oxalate is added into the water to uniformly stir firstly, then the 18-niobium tungsten manganese phosphate is weighted and added into the water, and the obtained product is uniformly stirred. The application method is implemented through the steps of when the catalyst is used, adding the catalyst into coking wastewater in a ratio that the catalyst accounts for 0.1% mass percent of the coking wastewater, and then uniformly stirring the obtained product. The invention provides a catalyst and preparation and application methods thereof, and the catalyst is simple in formula, remarkable in effect, lower in cost, simple in application method, and suitable for pyrolyzing coking wastewater by using converter high-temperature flue gas; and by using the catalyst, the pyrolyzing efficiency of coking wastewater in converter high-temperature flue gas can be effectively improved.