During the production process, the waste gas from paint evaporation is collected and preheated to 400 degrees before catalysis, and then catalyzed by palladium based honeycomb ceramic catalyst. After the catalytic combustion, the high temperature thermal air flow is generated. Most of the heat energy is sent into the furnace evenly through the circulating fan, and the heat energy is reused. The temperature in the furnace is replenish, and the energy saving effect is achieved. Another part of the heat energy is added to the catalyst before heat to meet the needs before heating through heat exchange, which greatly improves the combustion and purification rate of the catalyst. Then, the exhaust gas blower is used to discharge the purified gas out of the workshop, so as to achieve excellent environmental protection effect.