Abstract: According to the technical requirements of GB/T 228.1-2010, the test methods of percentage elongation after fracture of metal materials usually include manual measurement and automatic measurement with extensometer. Because the testing machine could not clamp the extensometer with a gauge distance of 25 mm purchased directly during the tensile test of beryllium material, in order to meet the technical requirements of the standard for the use of extensometer, the blade of extensometer was redesigned and the test results were compared with the manual measurement results. The results show that the improved extensometer could be used to measure the percentage elongation after fracture of beryllium samples accurately and rapidly.