Lubrication system contaminated by cooling water in high-speed wire rod production line is the most common problem in domestic high-speed wire rod units at present. The electrochemical impedance spectroscopy (EIS) sensor is used to monitor the moisture content of lubricating oil of high-speed wire mill in real time, and the design of the installation position of the sensor is introduced. The on-line test results show that the sensor can accurately detect whether the lubricating system of the rolling mill is leaking, and can monitor the changing trend of water content in the lubricating oil in real time and send out an early warning to prevent abnormal wear, damage or burning of the friction pairs of the rolling mill.