Abstract: Salinity is one of the main parameters in marine hydrological surveys, and the verification of sensor data is an important step in data quality control. According to the Chinese National Standard-“Marine Survey Specification (2007)”, conductivity, temperature, and depth (CTD) data should be verified daily in a relatively uniform water layer. In this study, the CTD salinity data from a two-month field survey conducted at the end of 2023 in the western Pacific Ocean were compared and analyzed using on-site AUTOSAL 8400B measurement. The results confirm that the CTD salinity sensor was in a stable state during this survey. Through data comparisons, we found that the CTD salinity sensor and laboratory salinity meter exhibited good consistency in the deep-water layer below 600 m and the upper layers at 5 m and 25 m, which meets the requirements of National Standards. However, only the deep layer below 600 m is suggested to be selected for salinity comparisons because the thickness of the upper mixed layer in the study area exhibits seasonal variations between 10 m and 30 m, according to the results of earlier studies. Additional research is necessary to determine whether the 5 m and 25 m water layers in different seasons can be used for comparison.