Abstract: A variety of detection methods, such as single antenna radar, antenna array radar and self-assembled double antenna radar, are used to compare their capacity to identify deep steel bar of bridge. Firstly, the basic principle of radar detection bar is introduced, and then the effect of antenna spacing on the detection effect of deep steel bar is verified by self-organizing double antenna radar. The effect of three kinds of radar on deep steel bar is analyzed by indoor production of reinforced concrete specimen model. The results show that the positioning effect of the single antenna on the deep prestressed steel bar is poor. The self-assembled double antenna and the commercial antenna array equipment can detect the deep prestressed steel bar in the presence of the surface steel bar shield. Therefore, the self-assembled double antenna can be used instead of the expensive antenna array radar equipment to detect deep prestressed steel bar, and self-assembled double antenna can control the spacing of transceiver antenna, whose flexibility is of better and more practical value.