The flashover of icing insulator string is one of the severe problems for transmission lines. To study thefactors that influence the flashover characteristics of icing porcelain long rod insulator

the artificial icing and ACflashover tests are carried out on long-rod porcelain Insulator de-energized and energized in artificial climatechamber. And the influence of the flashover characteristics on the icing morphology

the equivalent salt depositdensity（ESDD）

and the icing water conductivity are also explored. The process of flashover is recorded by a high-speed digital camera and the leakage current and flashover voltage are recorded by the Oscilloscope. The test resultsindicate that the icing morphology makes the initial position and development of the arc different. And at the samevoltage the leakage current of the energized icing insulator is higher than that of de-energized icing insulator. Theflashover voltages almost decrease with the increase of ESDD and the icing water conductivity. In the meantime

theflashover voltage of the energized icing insulator is higher than that of icing de-energized energized icing insulator.The research results can provide foundation of examination and technical reference for the selection of insulators fortransmission lines and anti-icing and disaster reduction.