Abstract: Ultrasonic inspection of the baffle bolts, which are an important part of the internal structure of the reactor core, is faced with difficulties due to structural characteristics of the fastening pin, the complex structure of the contact site in the testing, and the limited space for contact coupling of the probe. In order to effectively identify the bolt thread reflection signal and the bolt shoulder defect, an innovative probe design and signal analysis method was initiated for the wall bolts. Blind test was performed by the inspection system for real bolts and it was shown that the examination sensitivity was relatively high.