Abstract: The post-construction stability monitoring of breakwaters is one of the key tasks to their operation, and a large amount of measured data needs to be required for the stability and safety analysis. The traditional methods such as leveling and GPS are time consuming and labor-intensive, which only provide sparse points. The PSI technology can obtain the high-density target points and the line-of-sight (LOS) deformations through monitoring the distance changes between the radar sensor and the ground targets (such as artificial buildings, roads, and other infrastructures). PSI is suitable for monitoring the areas where long-term slow deformation occurs. Taking a breakwater (8 km) in Lianyungang as an example, a total of 38 C-band images of Sentinel-1A, from September 29, 2016 to December 29, 2017, are analyzed and 788 persistent scatterers (PS) are extracted. Nine feature points are selected to analyze the deformation pattern. The results show that the cumulative settlement of the breakwater reaches 336 mm, which accounts for 0.8% of the breakwater height, indicating that the dike is safe and stable. Finally, by comparing the PSI with the leveling during the same period, it can be found that the two monitoring results are consistent and can meet the accuracy requirements of the breakwater settlement monitoring, which performs the great potentiality in monitoring the settlement of linear engineering.