According to the fracture failure of sub-conductor of 6-split conductor in 500 kV transmission line, the material test, finite element simulation and comprehensive analysis of fracture failure were carried out. The analysis results show that the sub-conductors fracture failure are caused by the shear fracture of partial aluminum wires due to the shear stress of conductor torsion, as well as the combined effect of dynamic tension formed by ice-shedding and icing static load. Based on the research results, this paper proposed the corresponding measures for the operation, maintenance and reformation, which could provide reference to avoid similar failures.