Abstract: In sulfur dyestuff industry,a large number of dye wastewater will be generated when using sodium sulfide to reduce nitryl into azyl.If this high-chroma,strong reducing material contained wastewater was discharged directly without any treatment,the environment (surface water,ground water,and air) will be seriously polluted.Introduced qualified industrial-grade sodium thiosulfate was prepared by Barium Product Branch of Nafine Chemical Group through the method of using sulfur black wastewater to prepare sodium thiosulfate.Method is through the procedures,such as decolorization,flocculating settling,evaporation concentration,filtration,crystallization and dehydration to treat sulfur black dye wastewater,and the process conditions were as follows:adjusted pH at about 6,controlled solution density at 1.530 2~1.563 4 g/mL,temperature at 40~47 ℃,and crystallization time for 8 h.This mehtod not only solved the problems of sulfur dyestuff wastewater treatment and environment pollution,but also created economic benefits for the company.