Abstract: The corrosion and fracture of bolts on gantry cranes in nuclear power plants affect the overall structural safety of the gantry crane steel structure, delay outages for nuclear power plants, and pose a risk of falling and injuring people. Currently, manual inspection of high-altitude bolts on gantry cranes was carried out using scaffolding, which was inefficient. This paper presented an inspection solution specifically designed for high-altitude bolts on gantry cranes in nuclear power plants based on actual plant requirements. The solution employed phased array ultrasonic testing to test internal defects in bolts, visual recognition to identify abnormalities on the surface and surroundings of bolts, and electromagnetic ultrasonic measurement to assess the axial force state of bolts. The research developed a high-reliability precision inspection device for high-altitude bolts on gantry cranes in nuclear power plants, achieving miniaturization of the inspection equipment. Through the UAV equipped with intelligent manipulator, phased array ultrasonic inspection module, electromagnetic ultrasonic axial force measurement module and visual defect recognition module, the high-reliability and accurate automatic inspection of nuclear power plant gantry bolts was carried out, and the inspection period of high-altitude bolts of gantry frame was greatly compressed.