Abstract: The strain clamp of high-voltage overhead transmission line is taken as the research object, and the stress analysis is carried out by using Ansys finite element software. The stress distribution state of strain clamp of in-service transmission line is obtained. Combined with the actual crimping situation of the strain clamp project, the strain clamp samples containing a variety of typical defects such as pressure leakage of aluminum tube positioning slot, insufficient insertion of steel core, aluminum strand breakage and so on are produced, and the strain clamp crimping quality is tested by phased array ultrasonic testing and X-ray digital imaging. According to the test results, different characteristics of the two test methods are compared and analyzed. It is concluded that phased array ultrasound has the characteristics of accuracy, efficiency and no radiation hazards for the crimping quality test of strain clamps. This technology provides a scientific basis for the in-service inspection and evaluation of the crimping quality of the strain clamps of transmission lines.