Abstract: Applying bubble model in DELFIC, Davis-Stokes-Beard equations and Kolmogoroff Batchelor theory, a computer procedure was developed to predict local fallout after a ground nuclear detonation. This work focuses on the activity distribution of three different fractionation models and their effects on local fallout prediction in the case of a given particle diameter distribution. The results show that F-T model is more accurate than G-X model and Miller model, and the mean absolute relative deviations are 28%, 45% and 35% respectively. Fractionation model plays an important role in local fallout prediction.