The principle and process flow of hydrolysis on desulfurization wastewater by vacuum potassium process are described.Operating conditions of the hydrolysis unit for desulfurization wastewater of Ansteel Chemical Technology Co.，Ltd.are introduced after it was put into production. Besides, the lab report on CN- of the desulfurization wastewater before and after the hydrolysis is analyzed.The result shows that the hydrolysis process has a higher efficiency for total CN- removal,up to 99% in lab condition and 97% in actual operation.It can be put into commercial production in safe,stable and continuous manner.