The sonic echo test is a regular nondestructive test, and the applications are mainly limited by piles with high length-to-diameter ratio, high soil shear modulus, small defect areas or with an inaccessible head condition. Wavelet transform (WT), however, has good time frequency characteristics, which is suitable for identifying the singularities of pile testing signals. Three-dimensional axial symmetric finite element models were used to simulate the testing, and wavelet transform was employed to deal with the simulated signal data. It was found that for piles with accessible head condition, wavelet transform can identify weak wave reflected from pile bottom or defects, then reduce the limitation of length-to-diameter ratio, soil shear modulus, defect areas; For pile with inaccessible head condition, pile bottom can be identified by plate-excitation if the plate is within certain effective sizes.