Abstract: A new interpretation method, namely time domain segmentation spectrum analysis method, is proposed by conducting on-site geological radar experiments on two limestone and half limestone mediums. The method firstly performs time domain segmentation on the radar data detected on the spot, and then performs spectrum analysis on each time domain segment separately. The experiment found that the complete limestone chromatogram in the 0 to 300 ns time domain, the high amplitude frequency is mainly concentrated in 50 to 70 MHz, in the 300 to 600 ns time domain, the high amplitude frequency is mainly concentrated in the 15 to 35 MHz, which is shown as a horizontal high amplitude band on a chromatogram; in the semi-air semi-limestone medium, the chromatogram of the limestone still has a horizontal high-amplitude band phenomenon, while in the air part, the high-amplitude frequency distribution on the chromatogram is disordered. The results are compared and verified in the field. The results show that the horizontal high amplitude band in the chromatogram can be used as a basis for discriminating the development of hollow caves in karst tunnels, which can effectively reduce the construction risk of empty caves to tunnels.