To study the distribution of ground electric field for UHV AC transmission lines and the effect of corona discharge on the ground electric field, we built an electric field strength calculation model of line considering corona effect by improving the calculation method of power frequency electric filed based on charge simulation method. The model was proved to be reasonable through example analysis. The ground electric field of 1 000 kV UHV transmission line under the effect of corona discharge was calculated by the model. The results show that the corona discharge can enhance the ground elect...