An numerical simulation experiment was conducted on a large-scale hail weather process in Guizhou on 2 April 2018 to assimilate C-band Doppler radar reflectivity data by using the Newton continuous relaxation approximation method (nudging) based on the high-resolution numerical model in South China. The analysis results show that the hydrometeor information and the thermal field structure got adjusted after the nudging assimilated the radar reflectivity factor in the model. The content of rainwater and ice particles in the middle troposphere increased, and the latent heat release of the hydrometeor heated the cloud body and adjusted the positive temperature disturbance for the atmospheric thermal field. This kind of positive temperature disturbance plays an important role in maintaining the development of convection. The cloud analysis system was used in reversing the microphysical quantity, then the nudging assimilated the reverved cloud microphysical quantity into the initial field of the model. Thus, the hail cloud development and evolution, hail cloud life and hail cloud intensity have all improved significantly. The conversion process of cloud water to ice-phase particles in the cloud has been promoted, which has made a significant contribution to the improvement of precipitation forecast effect. Therefore, the assimilation of radar reflectivity factor is of great significance to the forecasting ability of the hail cloud weather system, and could provide an important reference for nowcasting hail clouds.