A new compact ground penetrating radar system has been built and an android application of realtime signal processing has been developed with Java language in the demand of reinforced concrete detection, which can help the engineers to work efficiently and conveniently. The radar data would be received in real time, and be drawn into singlechannel oscillogram and grayscale images, and stored in the SD card. At the same time, a realtime steel rebar recognition algorithm has been proposed and applied to signal processing client, realizing automatic identification of the target in reinforced concrete structure. Experiments show that the algorithm has high accuracy and good realtime performance.