Abstract: Circumferential exposure technology of X-ray detection is increasingly applied to pressure vessel, boiler and pipeline radiographic inspection because of its 360°exposure one-time, high exposure efficiency and high crack detection rate. With the increment of focal length of the ray incident, the ray intensity decreased significantly. When it is under the same exposure conditions, how to choose the X-ray tube voltage and exposure time becomes a difficulty of the long focal distance circumferential exposure technology. In this paper, the application of the long focal distance(F=10 m) circumferential exposure technology in two low-temperature storage tanks was introduced as an example.