Abstract: A fracture accident occurred on a 220 kV transmission wire. The reasons of fracture were analyzed by macroscopical observation, margin size measurement, fracture analysis, breaking force test, chemical composition analysis and so on, and the influence of crimping process parameters on transmission wire breaking force was also studied. The results show that the steel anchor hoop was not pressed or the number of compression joints was insufficient, the tensile force of the wire will be significantly reduced,and the stress state of the wire will also be changed, which makes the steel core with relatively low strength at the outlet of the steel anchor became the maximum force position. Then the steel core was fractrued by force, led to the fractune of the transmission wire.