Abstract: A new technique of deriving three dimensional wind fields is investigated from the Dual-Doppler weather radar radial wind which is based on the Cartesian space using variational method. It provides a simultaneous resolution of three wind components and satisfies both the minimal dual-equation system and the continuity equation. The most advantage of this method is that can remove the potential draw back of an iterative solution of Cartesian dual-Doppler analysis techniques (It is a major demerit that retrieves the vertical velocity using mass continuity equation with iterative method). The data pre-process technology and interpolation are also studied. We developed a three dimensional Cressman weighting function to process the interpolation. In order to test the capability and advantage of this method, one numerical experiment based on simulate radar observations is designed. Firstly, we synthesize the dual-Doppler radar radial velocity and reflectivity from the numerical model. Then, the three dimensional wind components are retrieved from the radial velocity and reflectivity using this new technique. The retrieved three-dimensional wind fields are found to be quite consisted with those previously simulate winds fields. Mean difference, Root-mean-square error and relative deviation are defined to test the precise of the new method. These statistic errors reveal the accuracy and the advantage of this method. The numerical experiment definitely testifies that this new technique can be used to retrieve the three-dimensional wind fields from the radial velocity and reflectivity detected by the real Dual-Doppler weather radar.