The changes of particle size distribution were investigated during the rapid growth of particles in the silane plasma reactor by the discrete-sectional model. The particle size distribution becomes bimodal in the plasma reactor and most of the large sized particles are charged negatively, but some fractions of small sized particles are in a neutral state or even charged positively. As the mass generation rate of monomers increases or as the monomer diameter decreases, the large sized particles grow more quickly and the particle size distribution becomes bimodal earlier. As the mass generation rate of monomers decreases, the electron concentration in the plasmas increases and the fraction of particles charged negatively increases. With the decrease in monomer diameter, the electron concentration decreases in the beginning of plasma discharge but later increases.