Abstract: The four-dimensional variational assimilation of Doppler-radar data (4DVAR) in theory was analyzed. Its main course and basic ideas were discussed. Then the four-dimensional variational Dopple radar analysis system (4D-VDRAS) was emphasized, the cost function was defined, and conjugate formulate and simile adjoint were applied to educe its minimum. In addition, radar disposing and Barnes insert technique were introduced. The application of 4D-VDRAS was discussed.