Relates to a catalyst temperature estimation method of the present invention a catalytic converter overheating protection area in accordance with, the method for detecting the cooling water temperature, conditions comprising the steps of: determining whether reaching the COP region on the basis of the cooling water temperature, has not reached the COP region in determining a catalyst temperature predicted value plus the weight and the weight in accordance with a spark timing in accordance with the air-fuel ratio in the main catalyst temperature predicted value, in reaching the COP region status weighted according to the weight, the spark timing of the air-fuel ratio in the main catalyst temperature predicted value, and and determining a catalyst temperature predicted value plus the weight of the cooling water temperature, according to the catalyst temperature prediction value is configured to include a step of adjusting the air-fuel ratio, higher than the actual in accordance with the cooling water on the catalytic converter overheating prevention area upon entering the catalyst temperature predicted value by to predict, to make rich the air-fuel ratio to improve the cooling performance.