To better understanding of the sustaining snowfall occurred in Shandong on 14—16 February 2005,the PSU/NCAR MM5 model is used to replicate the process. The simulation results show that the start, evolvement and duration the event agree well with the observation although some shortage exist. On the basis of success simulation, the conditions of vapor and evolvement of cloud microphysics parameter in the process are analyzed with the model output data, especially the quality content of ice(Q_i), graupel(Q_g), snow(Q_s), cloud water(Q_c) and rain water(Q_r) calculated with Reisner graupel scheme. The results show that the sustaining snowfall is based on the vapor supply from SW and SE winds, the development and evolution of the shear-line and intermediate cyclone on 850hPa.The simulated velocity and cloud microphysics fields show that vertical motion is dynamics factor causing the vapor condensation and freezing, and ice particle increase. The opportunity of artificial seeding in different condition is also discussed.