Abstract: The insulator flashover caused by icing seriously threat the security and stability of power system. In this paper, the experiment of insulator flashover caused by icing is carried out at ultra high voltage (UHV) AC experimental base. The leakage current signal of icing insulator is studied by bi\|spectrum analysis method, and the parameterization bi\|spectrum figures of leakage current at different stages are extracted. Results show that the maximum spectrum value of insulator presents increasing trend, the coupling region of quadratic phase is decreasing, and the distribution becomes more concentrated. The bi\|spectrum theory will be new guidance for warning of icing flashover section, which is beneficial for build icing flashover warning system.