Turbulent exchange is one of the key physical processes in sea fog formation, development and dissipation, and plays an important role in the heat and water vapor balance in the fog layer. Based on in situ observation of a sea fog event during 24－25 March 2007, the characteristics of turbulent heat flux and its effect on fog evolution were examined by distinguishing the turbulent heat transport induced by wind shear and by fog-top longwave radiation cooling. Results show that: (1) the observed sea fog occurs over the cold water near the coast of the South China Sea (SCS) and results from advection of warm and moist air from the Philippine Sea, which is under the control of the low pressure in Southwest China and the transformed cold high pressure over the ocean. The turbulent heat exchange associated with the warm sea fog is more complicated than that during the cold sea fog. (2) During the formation and dispersion phase of the warm sea fog, the heat transport is primarily induced by wind shear, whereas during the development/persistence phase, the turbulent heat transport is induced by both the wind shear and the longwave radiation cooling at the fog top. (3) The wind shear-induced turbulence transports heat to the sea surface, favoring cooling and moistening of the air near the sea surface. The heat transport resulting from the fog-top longwave radiation cooling also transports heat downward but warms and dries the air in the sea surface layer. (4) The mechanism of heat exchange during the warm sea fog has a close relationship with the immature mixing structure in the fog layer.