Abstract: The reasons of scaling in the ammonia stripper for the ammonia and nitrogen removal from the ammonium vanadate precipitating waste water were discussed in this paper. The main cause was found to be the formed calcium and magnesium scaling in the ammonia stripper by the complex chemical reactions between the calcium & magnesium ions and carbonate,hydroxide,silicate ions under high temperature and alkaline conditions. The countermeasures for solving scaling were also proposed as follows: ①Adding the scale inhibitor KL101 to vanadium precipitation wastewater with weight ratio of 0.02%; ②Regularly cleaning the pipelines,heat exchangers and Pall ring in the ammonia stripper. After the implementation of the measures mentioned above,the operating period of the ammonia stripper increased from less than 7 days to more than 40 days,which achieved long-term,safe and stable continuous operation with less than 30 mg /L NH₃-N in the waste water after ammonia removal and satisfying the discharge standard.