Comprehensive marine atmospheric turbulence observation data, meteorological sounding and sea surface conditions in the South China Sea were employed to analyze and parameterize the vapor profile in the stable marine atmospheric boundary layer. The observations involved a three-dimensional ultrasonic anemometer, water vapor carbon dioxide analyzer, radiosonde and buoy. This paper theoretically determined that the water vapor profile function φ_q differs from the temperature profile function φ_h and that φ_q should be independently parameterized. A linear relationship existed between the dimensionless water vapor gradient and stability parameters based on the observation results, and φ_q was then obtained as φ_{q(z/L)=a(z/L)+b}, in which the stability covered the stability range (z/L>1). This result was applied in the Tropical Ocean-Global Atmosphere Coupled-Ocean Atmosphere Response Experiment (COARE) bulk flux algorithm, and the simulation of the latent heat flux was improved.