Abstract: In the early stage of subway construction, the detection of underground diseases is particularly important. This article starts from a brief introduction to the working principle of the geological radar method, and combines engineering examples to analyze the characteristics of geological radar images generated by different underground media The detection profile is drilled to verify the effectiveness of the ground penetrating radar in the detection of underground diseases in the early stage of subway construction. Finally, according to engineering practice, the problems that should be paid attention to in the detection of underground disease bodies by ground penetrating radar are given to provide reference for the construction of similar projects