Based on the existed threedimensional convective cloud model, a homogenous freezing and heterogeneous nucleation scheme is newly implanted. Combined with a single mountain thunderstorm case, some sensitivity tests are used to investigate the impact of atmospheric ice nucleus concentration on microphysical processes and precipitation. Simulation results show: (1) The change of ice nucleus concentration will affect the dynamic field of the convective cloud and all the hydrometeors. As the concentration of ice nuclei increases, the concentration of ice crystals increases, and a large amount of latent heat is released during the condensation process, which leads to an increase in the vertical updraft. At the same time, the concentration of graupel particles in the cloud becomes larger. However, due to the limited water vapor content, each of the hydrometeors particles “races for” water vapor, the growth of cloud droplets, ice crystals and graupels is suppressed, and it is difficult to become a largersized precipitation particle. (2) The increase of ice nucleus concentration leads to the reduction of the scales of cloud droplets, which weakens the process of automatic conversion of cloud droplets into raindrops. The decrease in the mixing ratio of raindrops and cloud droplets inhibits the collection of droplets by raindrops. At the same time, smallscale graupel particles weaken the process of melting graupels into raindrops, which ultimately leads to a reduction in cumulative rainfall on the ground.