Abstract: Seawater intrusion problem has spread to the nine coastal provinces of China, the invasion areas of Shandong province and
Liaoning province have exceeded 2000 km2. The problem of seawater intrusion is unavoidable under the influence of climate change
and human activities. Therefore, the monitoring and prevention of seawater intrusion are significant to solve the problem. In this paper,
the fiber Bragg gratting (FBG) method for large-scale real-time in-situ monitoring of seawater salinity is proposed, and the feasibility of
three FBG salinity test plans is compared and studied by the designed experiment. The experimental results show that FBG technology
is feasible for seawater salinity monitoring; The FBG test with energy compensation technique is the best, and its sensitivity and
stability are the best in the three plans. The salinity monitoring method based on FBG can make up for the shortcomings of water
chemistry and geophysical methods, and provide an advanced and efficient way for monitoring and preventing seawater intrusion.

Key words: salinity monitoring, seawater intrusion, fiber Bragg grating (FBG), experimental study, feasibility