The invention relates to a method and a device for processing waste water in production of pyridinium. Industrial wastewater enters a single effect evaporator from the top of the single effect evaporator, part of ammonium hydroxide is distilled by a heater, the temperature of the single effect evaporator is controlled to be 80-90 DEG C, the wastewater processed by the single effect evaporator enters a kettle-type evaporator for secondary treatment, the vacuum degree is below 0.08-below 0.10MPA, the temperature is controlled to be 60-70 DEG C, the wastewater (ammonium hydroxide) is evaporated to dryness so as to extract ammonium salt, and low concentration ammonium hydroxide evaporated by the single effect evaporator and the kettle-type evaporator returns back to a production system to be recycled. The method has the advantages of effectively using the waste heat of other workshops, reducing the damage of the waste heat to climatic environment, simultaneously processing high-salt high ammonia-nitrogen wastewater generated in the workshop, being capable of recycling the recycled low concentration ammonium hydroxide and waste salt, and reducing the damage of the ammonium hydroxide and waste salt to the environment.