Flashover of ice-covered in power grid. As leakage current suspension insulator string is one of the is one of the important characteristics to major problems for the transmission lines predict the flashover of suspension insulator string, measuring method and analysis of the leakage current are developed for ice-covered XWP2-160 porcelain suspension insulator string in this paper. The waveform of the leakage current is perfectly recorded from the occurrence of micro-discharge to flashover, in which the process can be divided into four periods according to the evolution of the leakage current. There are different rising rates of the leakage current and various phenomena of arc discharge in different periods with the increase of the applied voltage, and the distortion on the leakage current waveform is detected because of the effect of arc discharge. A characteristic current （Iw）and a critical current （IFT）of flashover, two important parameters of the leakage current before ice-covered insulator string flashover, are defined for analysis of the leakage current characteristics of pre-flashover along the polluted insulator string covered with ice. Statistical experimental results show that the average values of Iw and IFT are within the major distribution zones, and both currents can be used for predicting the icing flashover. The values of two important leakage currents are approximately constant at different contamination degrees, while the direct relationships between the critical currents and the contamination degrees are not found in this paper.