Based on 26 days of Chinese Sea-wing underwater glider measurements and satellite microwave data, we documented cooling of the upper mixed layer of the ocean in response to changes in the wind in the Northern South China Sea (NSCS) from September 19, 2014, to October 15, 2014. The Sea-wing underwater glider measured 177 profiles of temperature, salinity, and pressure within a 55km×55km area, and reached a depth of 1000m at a temporal resolution of ~4h. The study area experienced two cooling events, Cooling I and Cooling II, according to their timing. During Cooling I, water temperature at 1-m depth (T1) decreased by ~1.0°C, and the corresponding satellite-derived surface winds increased locally by 4.2m/s. During Cooling II, T1 decreased sharply by 1.7°C within a period of 4 days; sea surface winds increased by 7m/s and covered the entire NSCS. The corresponding mixed layer depth (MLD) deepened sharply from 30m to 60m during Cooling II, and remained steady during Cooling I. We estimated temperature tendencies using a ML model. High resolution Sea-wing underwater glider measurements provided an estimation of MLD migration, allowing us to obtain the temporal entrainment rate of cool sub-thermocline water. Quantitative analysis confirmed that the entrainment rate and latent heat flux were the two major components that regulated cooling of the ML, and that the Ekman advection and sensible heat flux were small.