Abstract: Based on the analysis of procedure of bolt tensile test in the national standard GB/T 3098.1-2010 “Mechanical Properties of Fasteners-Bolts, Screws and Studs”, it was found that the effective length of thread engagement was one of the key factors that affected the test results. However, there was no requirement for maximum length in the standard. Therefore, it might cause distortion in the test results of load-carrying capacity of thread.