Abstract: Reactor pressure vessel bolt is one of the important parts of nuclear equipments. The pre-service or in-service ultrasonic inspection is needed according to RSEM standard. This inspection can be finished by several system including ultrasonic inspection system, mechanism scanning system and control system. The article introduces the inspection feasibility of improved reactor pressure vessel bolt, the inspection position, the choice of probe, instrument and scanning method, acquirement and analysis system. The testing result is accordant with the request of ultrasonic inspection of improved reactor pressure vessel bolt.