Abstract: In-service ultrasonic examination shall be performed the key components(such as RPV and SG) of Nuclear Power Plant in order to detect service-induced defects in the nozzle inner radius and bore region. Due to complex geometry, the development of ultrasonic examination technique of nozzle inner radius has always been a challenge. This article mainly introducs ultrasonic examination technique of inner radius from inner surface and outer surface according to ASME code requirement, and then discusses the effective technique for inner radius ultrasonic examination based on research development of our company.