Abstract: On the basis of Harriott’s theory,a new mass transfer model was presented.It expanded the working point of eddy in falling-film absorption from a geometric point to an area,and divided the whole flow into a turbulent flow zone and a non-turbulent flow zone.When the flow was non-turbulent, Levich thickness was handled in different ways in wave trough zone and wave crest zone.The velocity of wave motion was amended in the turbulent flow zone.The deviation between the model and experimental data of ammonia water falling-film absorption on a smooth vertical tube was not more than 10% in the turbulent flow zone and 15% in the non-turbulent flow zone.The influences of diffusion coefficient, Levich thickness and wave period on mass transfer coefficient were expressed correlation as the relation of two non-dimensional numbers.