Abstract: The snowfall that occurred in Beijing from 05:00 to 17:00 BT 17 March 2018 is simulated using the Weather Research and Forecasting (WRF) model to study the main influencing mechanism of urbanization on snowfall. Results show that urbanization in the metropolitan area of Beijing can reduce snowfall and increase rainfall,which is largely attributed to the fact that the low-level warming effect of urbanization strengthens the melting process of snow,producing more mixed-phase precipitation. Areas closer to the city center are prone to more mixed-phase precipitation. Urbanization also affects spatial and temporal distribution of total precipitation. At the beginning of the precipitation process,the "urban dry heat island" effect induced by urbanization is not favorable for horizontal and vertical transport of water vapor and the formation of clouds,and thereby the total precipitation would decrease. As the precipitation process develops,some ice phase particles melt and the water vapor in the near-surface layer increases. The thermal uplift effect of the "urban heat island effect" is conducive to vertical transport of water vapor and the development of clouds. Cloud droplets and/or water vapor rise into the clouds,enhancing the cold-cloud process. The cold-cloud process leads to more snow and graupel particles and increases total surface precipitation. The "urban effect" generated by urbanization has impacts on low-level atmospheric temperature and cloud microphysical processes. The non-adiabatic cloud microphysical process in turn affects lower atmospheric temperature and atmospheric stratification as well as the energy and water vapor transport,which subsequently influence cloud and precipitation.