Ground Penetrating Radar is an intact sounding technology in archaeological research field. It has constructive significance especially in positioning underground ancient relics or other remains and deciding the distribution area. The EM

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aves can’not reach deep into the underground in the Yangtze down

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iver area because it is absorbed by plenty of moisture for the high underground water level and the wet earth. This fact results in the shorter penetrating altitude and less precision for the back

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ave shorter altitude and lower S/N rate. For the stratum is a kind of chromatic dispersion media

the radar back

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ave impulse become broader after it come across stratum. The back

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ave can be identified correctly and the precise position can be stated which make it difficult to define the project exact location and profile in the latter data processing and image rebuilding process. This article presents a new method that is encoded by both impulse signal and FMCW radar signal to positioning the underground ancient relics especially the vault tombs under the special geographic conditions like the Yangtze river. It increased the signal S/N rate by the vertical time related technology to enhance the penetrating precision. The profile of the underground tombs is determined by the way of back

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ave energy related method to indentify the project location. The wave

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ransmitting antenna is located at different places and the reflection character parameters of the project are processed in collective grouping way. Then using image processing technique the underground relics is reversely

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educted in 3D and the error of the position is deduced to the minimum.