Abstract: The spill of the volatile poisons into natural waters causes water pollution and air pollution arises from the volatilization of water pollution. In order to explain the coupling of water pollution and air pollution, the dynamical model is put forward by using the volume of fluid method, in which there is gas-liquid interface flow term. According to the double-film theory explaining the volatilization, the dimensionless Henry constant of the volatile poisons is used to establish the coupling diffusional model in which the transport of the volatile poisons in water and air and mass transfer across gas-liquid interface are presented together. The spill of the volatile poison into the Mississippi River and a gas-water experiment are simulated. The simulation results are in exactly agreement with those of the experiment. The simulation analyzes the influence of the turbulence of water, wind velocity and the dimensionless Henry constant on the mass transfer across gas-liquid interface.