A method of predicting gas flow strength upon burden surface has been proposed in this paper. A frequency modulated continuous wave (FMCW) radar is employed to achieve the echo signal of burden surface. The radar, operating at 24–26 GHz, is mounted on top of blast furnace (BF). The burden surface scattering yields attenuation due to the burden surface dust. The propagation constant has been derived in terms of gas flow velocity, particle size, dust concentration and so on. The method has been validated in real blast furnace during production process and maintenance process, respectively. The experiment results show that the predicted value has close agreement with the measured value. The attenuation has the same periodic trend with the BF charging process.