A probability calculation method of broken lines and collapsed towers under ice storms based on generalized Pareto distributions（GPD） and Copula function is presented. Based on GPD of meteorological variables， such as wind speed and freezing precipitation， the probability calculation model of ice loads and wind loads on transmission lines and towers are proposed. Then a joint probability distribution model for ice and wind loads of power line and tower is put forward， in considering the dependence of ice loads and wind loads and based on Copula function. Furthermore， a probability calculation of broken lines and collapsed towers under ice storms is completed for historical data of 220 kV transmission system in Chenzhou power grid， Hunan. Comparing the calculation results with practice， it shows that the accuracy and validity of this model are quite perfect.