This paper describes the thermal lag correction for Glider Payload Conductivity Temperature Depth Profiler data with a poor sampling rate. In particular, the thermal lag correction is more vulnerable to the influence of temperature data. According to variations in salinity with depth and the vertical downcast speed of the glider, salinity data are divided into five parts, and a method based on Morison et al. is proposed to determine the correction parameters. At 40–94 dbar and 140–280 dbar, the salinity difference is dominated by the temperature difference. At 94–140 dbar, the salinity difference is immune to the temperature difference and has a greater influence on the thermal lag-induced salinity error correction. After the sectional correction, the accuracy of the typical salinity interval is upgraded from 0.011 to 0.006 psu, which shows the effectiveness of this sectional method on correcting temperature difference.