Abstract: In this paper, based on the analysis on the water quality of the desulfurization wastewater generated from a power plant, an in-depth treatment technology for the wastewater using low temperature flue gas waste heat flash is proposed. With the model of evaporation established and then solved, the main parameters of the process system were determined. Then a pilot-scale project with the wastewater treatment volume of 15 m³/h were built. The operation results show that the process system is simple in structure. And the operation is stable and reliable with low costs, high water recovery volume and basically free of wastewater discharge, which means that the goal of zero wastewater discharge has been achieved. In addition, the main quality indices of the wastewater after treatment have basically met the requirements of GB/T 50050—2017 "Code for Design of Industrial Recirculating Cooling Water Treatment".