Defect detection of porcelain insulators is an important link in line maintenance. Accurate detection of insulator cracks can avoid accidents such as short porcelain lines caused by porcelain insulator breakage. In the maintenance test of porcelain insulators of hV line, it is required to shorten the maintenance time as much as possible in order to restore power transmission as soon as possible. In this paper, a special fixture and a special curved probe for ultrasonic testing of porcelain insulators are developed to shorten the ultrasonic scanning time and the time of defect testing of porcelain insulators. Special fixture and special curved probe are made for ac prop porcelain insulators of 66kV and above voltage grade, and have become favorable weapons in electrical test work, greatly improving the work efficiency of transformer maintenance personnel and ensuring the normal operation of transmission lines. The shortening of testing time also reduces the line outage time, ensures the daily life and work of customers, and improves the power service level of enterprises.