Abstract: Aim In order to simulate the agglomeration of fly ash particles in the acoustic field more exactly, a new math model is constructed. Methods Referring to the result of the former researcher, the new model was set up using the theory of fractal geometry and verified by means of experimental results. Results Because of the self similarity of the agglomerated particles, which was found in the experiments of agglomeration for fly ash in the sonic field, the data from this method fit well with those from experiments. Conclusion The computing precision by this model was high due to the use of fractal geometry.