The upper ocean temperature and salinity responses to Typhoon Bavi (2008) are investigated using multi-source satellite remote sensing data, Argo float data, and HYCOM (HYbrid Coordinated Ocean Model) reanalysis data. The results are shown below. (1) Ekman pumping near the typhoon center causes upwelling, the seawater below the surface converges with high-salinity cold water and turns upward, the Ekman transport direction points from the typhoon track to the coasts on both sides of the track, and the seawater accumulates on both sides of the Yellow Sea and causes downwelling. This leads to a decrease in SST (sea surface temperature) and SSH (sea surface height) near the typhoon track, an increase in SSS (sea surface salinity), an increase in SSH along both sides of the track, and an increase in temperature and decrease in salinity of subsurface seawater. (2) Due to the higher wind speed on the right side of the typhoon’s heading direction, the intensity of Ekman transport on the right side is greater than that on the left side. As the typhoon is closer to the land on the right side, the terrain blocks the wind speed, the 10-m wind above the sea area on the southwest side of Jeju Island shows an anticyclone rotation, and a negative EPV (Ekman pumping velocity) appears, which is a downwelling. Therefore, there is a transition from strong upwelling to downwelling in the sea area between the typhoon and Jeju Island. This will further strengthen the strong entrainment and vertical mixing on the right side of the typhoon’s heading direction, leading to a more significant decrease in SST and an increase in SSS on the right side of the typhoon’s heading direction. (3) In addition to the entrainment and vertical mixing, the increase in SSS on the right side of the typhoon’s heading direction is also related to the horizontal flow of surface seawater from south to north.