This study introduces the rapid update cycle assimilation technique of C-band radar in Ningxia and its application to the rainfall forecast in the summer of 2018. The rapid cycling assimilation technology was mainly based on WRF(Weather Research and Forecasting) model, and through quality control of C-band Doppler radar such as removing singular point, ground object occlusion, spectrum width inspection and radial velocity unfolding，by the using of the three-dimensional variational data assimilation, dynamic downscaling technology and cold-warm start method, the C-band radar data hourly rapid cycling assimilation analysis was achieved.It could produce grid-point prediction products hour by hour in next 12 hours include precipitation, temperature, wind, relative humidity, physical quantity fields and radar echo with a horizontal resolution of 3 km.Through the application analysis in the precipitation forecast of Ningxia in 2018, it is found that the precipitation forecasting ability of WRF model with radar data assimilation is improved obviously. It can provide the technical support for the forecast of intelligent grid, especially the short-term and imminent forecast of heavy rain in Ningxia.