Based on the higher －order －statistics (HOS), a new method for identifying geologic cavities was introduced. By bispectrum time －frequency analysis (BTFA) to GPR signals, the variation of Gaussian properties generated from the geologic cavities to identify it was obtained. Theoretical and experimental results indicated that, the higher －order －statistics method is capable of recognizing the non－Gaussian signals under the disturbance of the strong Gaussian noise, and it can obtain clearer results than traditional methods when being applied to detect cavities.