For supersonic detection, the physical property of the measured media can be identified by using such kinds of acoustic information as the acoustic time, amplitude, frequency and waveform. The first three kinds of information can be measured based on quantitative or semi-quantitative mathematical expression, whereas the last one cannot be quantitatively interpreted. In order to study the variation of the waveform, the authors made a test by using the model test block. The test results show that the waveform of received signal is basically similar to that of the launching wavelet for the homogeneous media, which is consistent with acoustic boundary conditions. The mutation of received signal can result from the foreign body (defect) existent in the media. It can be explained based on the laws of refraction and superposition, so as to summarize some regularities and propose a quantitative method for quantification.