The invention provides a treatment method of catalytic 
cracking flue gas desulfurization 
wastewater. The treatment method comprises the following steps: fully utilizing 
waste heat of high-temperature 
flue gas, concentrating circulation 
slurry in a washing 
tower, and controlling the concentration of the circulation 
slurry, thus ensuring normal operating of a desulfurization 
system; meanwhile, carrying out pretreatment (flocculating, filtering, removing 
calcium and 
magnesium ions, reducing COD (
Chemical Oxygen Demand) through oxidization and the like) on concentrated discharged 
wastewater, enabling the 
wastewater to meet the feeding requirements of a concentration 
system, and then carrying out 
evaporation and 
crystallization (multi-effect 
evaporation or MVR (Mechanical Vapor Recompression)), thus realizing 
zero emission of salt-containing wastewater and recycling of inorganic salt. According to the technology, a 
sodium alkaline 
flue gas desulfurization technology and an inorganic salt evaporative 
crystallization recovery technology are organically integrated, the problems of membrane 
pollution and membrane scaling during a membrane concentration process, large investment, 
high energy consumption and the like are avoided, the emission problem of salt-containing wastewater in an alkaline washing technology is completely solved, and 
zero emission is really realized; meanwhile, separated 
crystallization is carried out on inorganic 
sodium salt products, the 
recycled products are used as products, the problems of mixed salt and 
hazard waste are solved, and secondary 
pollution is removed.