After predicting the dimensions of the karstic cavities from visible samples of Razak Formation in the south of Shiraz and then optimizing the design of the grids, the GPR recorder device with 100 MHz central antenna was used to identify the location and depth of these cavities. In order to eliminate the effects of unwanted low-frequency reflections on GPR sections, the Dewow filter, as well as the Gain function, was used to amplify the signals, especially at the ending times. In this survey, 50 profiles were collected in three blocks with whole profile lengths of 1,500 m. Then the collected data were processed by Reflexw software. The results of all profiles were illustrated with Auto CAD software, of which in this article the block number 2 and the processing results of this block are presented. The most notable case in this block was the identification of a hole with 2 m of diameter, located in depth of 2 to 5 m with 20 m of length that has identified during field visits.