The ground penetrating radar (GPR) detection as a kind of advanced nondestructive testing technology has been widely applied in engineering practice. The image of GPR is easily influenced by the surrounding environment; it is difficult to accurately judge the image of GPR in the complex conditions for the construction site. The laying of underground pipelines are scanned by GPR, and the radar imaging data are post-processed using Hilbert transform method through the field experiment in this paper. By the images contrasts, the characteristic point of the image are further described, the interference information is removed in a certain extent. The radar images of the special geological conditions are to make clear, specific and easy to identify. The distribution of underground pipelines from radar images are simulated by mathematical models finally, the boundaries of pipelines are determined to reliable identify. © 2014 ejge.