Abstract: In recent years, research efforts have been carried out to develop the radar data pre-processing system and assimilating strategy for the purpose of future operational implementation for BJ-RUCv2.0. There are 4 S-band and 2 C-band Doppler radars involved in this study, comprising the operation radar network in North China. A radar data preprocessing system was built on the base of the counterpart of VDRAS with the functions to perform quality control, mapping and error statistics. With techniques of tuning the background error covariance (BE) and length scales developed, a two-step scheme was designed to assimilate radial velocity along with other conventional observations. The pre-operational experiments of BJ-RUCv2.0 with assimilation of radial velocity were performed during the flooding season from 1 June to 31 August 2011. The results were evaluated and compared along with another identical experiment running in parallel but without assimilation of radial velocity. Monitoring on quality of the radial velocity data entering the data assimilation (DA) system revealed that the DA system effectively absorbed the information brought by the radial velocity and generated reasonable analysis increments. But obviously, the valid amount, data quality and reliability of radial velocity observations from S-band radars were much better than C-band radars. The evaluations for cycling forecasts for both experiments were performed against conventional surface and radiosonde observations. In general, from the 3-month results, no significant improvements were indeed found against conventional observations because of the localized impact of radial velocities in space and time. But more positive signals were shown by precipitation forecast skills, especially for short-term forecasts and the precipitations with larger intensities.The cases of a squall line and a local-forced convection were selected for more detailed discussion respectively. It was found that the more the assimilation time of radar radial velocity approached the occurrence time of convection, the more significantly the precipitation forecast skill was improved. For the well-organized convection such as squall line, the modification of low-level dynamical conditions brought by the assimilation of radial velocity was the key factor of the improvement of forecast. For the local-forced convections, the more favorable thermal circumstances were also built along with the modification of dynamical conditions. But it is still needed to be noted that, it is usually at the approaching time of convection that the effect of radial velocity assimilation gets to be more prominent.