Abstract: Ultrasonic detection can not only detect the internal defects of metal cylinder workpiece, but also be used for defect reconstruction and type identification. In order to analyze the regularity and characteristics of the internal defects of the cylindrical workpiece, a three-dimensional reconstruction analysis method of the metal cylinder based on ultrasonic detection was proposed in this paper. The finite element software was used to simulate, so as to simulate the cross-section signal of the inside of the metal cylinder. It then its pixels were reassembled by using B-scan imaging. Finally, volume rendering technique was used to reconstruct the defects. The simulation results showed that this method can achieve good results in the reconstruction and analysis of the internal defects of the metal cylinder workpiece, and the allowable errors met the requirements.