Research conclusions: From the testing instances，it can be seen that during the test it can not only use the sonic parameters to determine whether there is a defect in the pile，and various kinds of the parameters should be used together to determine whether there is a defect in the pile and what are the defect range and level． If the defects of the accumulation of aggregates and insufficient mortar caused by the concrete segregation exist，the sonic wave will pass the more interfaces to cause decrease of the amplitude． In the low strong area with the less aggregate and more mortar，the wave velocity is low，but the amplitude is basically the same，even over high． If the defects of the pile diameter shrinking and the pile with mud ( sand) exist，the sonic velocity and amplitude in this area decrease obviously compared with the normal concrete． The defect of lots of airs stayed in the concrete of the of the up part of cast － in － place pile caused by lifting the tube too fast will not produce the obvious decrease of wave velocity，but it will produce the obvious reductions ( scattering) of the sonic wave energy and the receiving wave energy．