The experiment of Shenyang Doppler radar data assimilation was mad e using WRF3DVAR system. The quality control system of Doppler radar data was developed. The 3DVAR system is able to assimilate both radial winds and reflecti vity directly, [JP2]not only can retrieve mesoscale 3D meteorological elemen t fields but also can offer initial fields to model. Thecan retrieve the mesoscale 3D structure of convective system in cold vortex well using synoptic sca le data as background field. The surface strong convective divergent flow and vo rtex in the middle troposphere retrieved were in accord with conceptual model an d th e wind fields retrieved were closed to surface observations. The meteorological element fields which have assimilated Doppler radar data can be offered to fore casting operation as real time analysis for they include mesoscale weather syste m. After assimilating radar case data of cold vortex over Northeast China, the model forecasts improved slightly for mesoscale and small scale convective syst em. Assimilating radar data made positive effects on model forecasts in general.