The atmospheric refractive section plane retrieved from radar sea clutter is of importance for the might enhancement of military naval radar. In this paper, an atmospheric duct signal processor with hardware of an intermediate-frequency board and a high-speed DSP board, besides the arithmetic of clutter suppression and sea clutter extraction, have been designed and implemented to get radar sea clutter power, which works synchronously together with a Doppler weather radar in the science experiment of atmospheric duct sounding. Results show that this signal processor can perfectly implement the acquirement of radar sea clutter and its real-time arithmetic processing.