In response to the national environmental policy, to improve the quality of water, the substation must strengthen the daily supervision of wastewater discharged and the management of online of wastewater. This paper introduces the source of waste water from substation, the analysis of key and difficult points in the treatment of waste water discharged from substation, and the of monitoring technology for waste water discharged from substation. The accuracy of the measurement results of the UV method COD analyzer was fully verified by analyzing the comparison of online monitoring system data and laboratory offline detection data and it can also quickly capture the trend of rapid changes in water quality after calibration. The problems of the online monitoring technology of the wastewater discharged from the substation and the new technology applied in the monitoring of the wastewater discharged from the subst are analyzed.