Abstract: Eddy current testing is the main detection method for the main bolts of pressure vessels in nuclear power plants. This method is mainly used for surface detection of defects at the root of threads. Line laser measurement technology is an emerging non-contact measurement method in recent years, which achieves large-area and high-resolution measurement of object surface morphology through high-speed laser scanning and has characteristics such as fast, non-contact, and high-precision, it is widely used in the field of industrial online measurement. Two methods were used to detect bolts, and the experimental results showed that both methods can effectively detect their defects. Line laser technology can be precise to the micrometer level, and the measurement results were more intuitive, easy to quantify, and qualitative. This provided reliable data support for defect determination in main bolt detection. Both detection methods had their own advantages and disadvantages, and in actual testing, their strengths and weaknesses should be complemented, thus providing a more intelligent and efficient detection scheme for the main bolts of reactor pressure vessels.