Abstract: The principle of inversion of water level changes using GPS signal-to-noise ratio data is described in detail. Comparing the water level change with the signal-to-noise ratio of the Calcasieu Pass GPS station and the data monitored by the tide station, they show good consistency. The correlation coefficient is better than 0.96, and the RMSE is about 8 cm. The results further validate the feasibility and reliability of monitoring sea level changes based on GPS signal-to-noise ratio data. Through the test and analysis of different periods and time length, it is proved that the shore based GPS station can continuously monitor the water level.