Abstract: Because of the interference of surface wave and noise, it is difficult to directly identify the reflecting layer's longitudinal wave from the spectral characteristics in detecting concrete structural defects by impact echo method. In response to this problem, this research introduces the complementary ensemble empirical mode decomposition (CEEMD) method into the impact echo detection signal analysis and proposes a CEEMD impact echo signal analysis method. The results show that the eigenmode function (Intrinsic Mode Function, IMF) IMF1~IMF10 decomposed by the CEEMD method from the impact echo through the simulation and experimental impact echo signal analysis, and research signal. The internal interlayer defect location and the thickness of the concrete slab can be applied to accurately determine the internal interlayer defect’s location and the thickness of the concrete slab based on the frequency spectrum. The CEEMD method can separate surface wave and noise interference, and can be used as a conventional method for processing impact echo signals.