Abstract: In view of the spectrum difference between seeding ice crystal and natural ice crystal,to improve 3D hail cloud numerical seeding model is improved: seeding ice crystal is treated as a separate predictand in the microphysics processes parameterization, and parameterization equations of processes which contact with seeding ice crystal are also deduced. After analyzing the seeding function of the improved model and the microphysics processes of seeding ice crystal, as well as its effect in hail suppression. The results show that the improved model′s seeding effect is better than the former model in the same seeding conditions. Nucleation of vapor on AgI is the principal process to produce seeding ice crystal. The spacial distribution of seeding ice crystal, it has a better condition to contact with cloud water and rain water than natural ice crystal, so collecting the super-cooled cloud water is the main difference in growing way between seeding ice crystal and natural ice crystal. Compared with the natural ice crystal，seeding ice crystal has a high converting rate into graupel and by it contact with supercooled raindrop a large quantity of freezing drops can be produced. Automatic converting process is the main processes to decrease seeding ice crystal. The mechanism of hail suppression is that a number of seeding ice crystal are produced by seeding, and so that graupel and frozen drops increased quantitatively, and amount of hailstone from converting of graupel and frozen drop increased, too. Thus, hailtone size is decreased, as a result intensity of hailfall and the kinetic energy flux of hailstone decrease.