Abstract: The application of tube to tube sheet fillet weld radiography technology(T-T-RT)can improve the product quality of heat exchangers and reduce the accidental leakage rate of heat exchangers in use. In recent years, the above-mentioned test method has been widely used in domestic applications, but its detection sensitivity is seriously out of control and needs to be closely concerned about. This article analyzes the factors affecting the sensitivity of T-T-RT technology, introduces the type, characteristics, and uses of a highly imitated type test block, and points out that improving quality awareness, in-depth study of technology and technology, and strict implementation of the detection sensitivity identification test in the standard to ensure the sensitivity of T-T-RT technology.