Abstract: An a tomization model for frefilming airblast atomizer is formulated on the basis of analysis and experiments,and put in to numerical computation.A breakup criterion of liquid film is provided to judge the film disintegration extent.Quantitative relations between the wavelength frequency spectrum of the film wave and its correspondingly formed droplet size number are consi dered.A Trace Statistical method is presented to perform the model computation.A numerical example of atomization of a three dimernsional axisymmetric atomizer has been completed.The consistence of the computational results with the experimental data demonstrates that this model is feasible.