Accident of icing induced line break occurred for the electric power transmissionline connecting Yucheng to Pugein the winter of 2011. Based on the observation and measured data, a broken section of the LGJ-630/45-type power line of stranded aluminum wires with steel core exhibited 12 broken aluminum wires with typical brittle fracture characteristics, but the rest wires were ductile fractured. On the basis of the theory of statics and dynamics of catenary beam element mode and large deflection bending beam element mode, the line breaking was analyzed by using ANSYS finite element method. Results show that the brittle fracture of 12 broken wires may be caused by fatigue, then the effective section of power line decreases, which further caused the rest wires to be broken due to overload. Icing and fluctuating wind lead the stress of the operating power line to be increased from 55.4 MPa to 97.9 MPa, which is the main cause to the line breaking. The power line resonate induced by the fluctuating wind, thus the mean stress of asymmetric fatigue increases, , and the fatigue life of the line significant decreases. Corresponding to all the above considerations, the realstress of the operating line increases from 97.9 MPa to 275.2 MPa and thereby the ductile fracture occurs due to that the real stress exceeded the failure stress of 221 MPa of the operating line.