Laser ultrasonic(LU) three-dimensional (3D) imaging system combining wavelet threshold method(WTM) was presented, in which a laser beam was used to irradiate the aluminum(Al) block as a scanner and an interferometer as a receiver. Ultrasonic signals saved were processed by wavelet threshold for reducing noise. And data processed constitutes a 3D matrix in the scanning sequence, which could be sliced along the time axis to yield spreadsheets and be superposed in a 3D space using the MATLAB procedure. Then, artificial defects can be modelled and visualized. Ultrasonic signals were incorporated with algorithm to successfully reconstruct the 3D object model, which could contain the defect information, indicating that laser ultrasonic 3D imaging is more intuitive and effective than the traditional laser ultrasonic method of identifying defects.