Abstract: The live testing of operating equipment has advantages such as safety and efficiency, and is widely used in substation operation and inspection work. However, many early defects and non electrical defects in the equipment are difficult to detect using conventional infrared and ultraviolet methods. Acoustic imaging technology solves this detection difficulty and can become a new live detection technology as a supplement to detection. This article introduces the principle of acoustic imaging, analyzes its advantages in practical work, and through on-site testing of substations, introduces practical cases of partial corona discharge, suspension discharge, insulation discharge, and mechanical vibration defects, providing reference for on-site defect identification of operation and inspection personnel.