Abstract: Salt tide invasion has always been one of the important factors threatening the water safety of the residents in the Guangdong-HongKong-Macao Greater Bay Area(GBA) and restricting its economic development. In order to monitor regional salinity accurately, efficiently and stably, the salt tide monitoring technology has developed from manual observation, fixed-point online automatic monitoring, and then to satellite remote sensing observation. The high-precision Conductivity-Temperature-Depth Monitoring System is a salt tide monitoring equipment based on high-precision and high-stability analog-to-digital conversion circuit. Its temperature resolution can reach 0.0001℃, conductivity resolution can reach 0.000 1 mS/cm, and its performance can reach the international advanced level. The application results of several stations in the GBA show that: It can accurately and stably monitor the chlorine content of water bodies, and is small in size and easy to carry, which improves the emergency monitoring efficiency of salty tides, provides technical support for the GBA to resist the invasion of salty tides and formulate measures to suppress salty tides and make up for desalinization, and has broad application prospects. In the future, satellite remote sensing observation technology can be considered to further improve the spatial scale of salty tide monitoring.