Abstract: Strain clamps are essential fittings in transmission lines, of which the neglected crimping of anti-skid grooves is one of the major failure factors. A failure accident of an NY-500/45 type strain clamp occured in a 500 kV transmission line,for which the possible neglected crimping of the anti-skid grooves was deduced by macroscopic feature, anatomic structure and fracture position analysis. In order to deeply explore the accident cause and failure mechanism, crimping-tension simulated experiments and finite element simulations were carried out in terms of various degree of the neglected crimping for anti-skid grooves. The results show that with the increase of the neglected crimping degree, the fracture position of the strain clamp is transferred from the aluminum strand near the end of the aluminum tube on the conductor side to the steel core at the exit of the steel anchor. The fracture position achieved by the finite element simulation is consistent with that of the experimental results, for which the relative error of the tensile failure force is within 5%. On the basis of the normalized stress distribution by the finite element simulation, with the neglected crimping degree increasing, the normalized stress concentration is shifted from the aluminum strand near the end of the aluminum tube on the conductor side to the steel core at the exit of the steel anchor, which therefore explains the law of the fracture position alternation by the increase of the neglected crimping degree for the anti-skid grooves. This work can provide theoretical and technological support for the safety operation of strain clamps.