Abstract: The impact of electric vehicles （EVs） on power grid can be refleced in the operation indices of power grid. Different calculation models and evluation methods were established according to the different evaluation indices in the process of research. The index system of EVs impact on power grid was presented in accordance with the existing grid operation indices. Considering the stochastic characterisitics of EVs charging load， the evaluation methods for the total requirement of charging load and impact on power grid were proposed. At last， the simulation calculation was carried out to the impact of EVs on power grid. The results show that the influence degree of EVs charging load on each index is variable. Besides the stochastic characterisitics of EV load， the correlation degree between the original load and EV load in time and space is also the important influencial factor.

Key words: electric vehicle, power grid, charging load, probabilistic power flow