Abstract: Electric vehicles (EVs) have attracted wide attention in the frequency regulation of power systems due to their increase in quantity and their fast response capacity. However, current research ignores the fact that during the frequency regulation their load attributes may lead to distribution network congestion when a large number of them are connected to the grid. Therefore, a control strategy for the supplementary frequency regulation with aggregated EVs is proposed considering distribution network congestion. Firstly, the hierarchical scheduling framework of the supplementary frequency regulation with the aggregated EVs is presented. Secondly, a frequency regulation power allocation mode considering the state of charge (SOC) of EVs is proposed. Then, a control strategy based on current congestion indicator factors (CCIF) is established to limit the charging and discharging power of EVs. Finally, the advantage of the control strategy is verified by the MATLAB/Simulink simulation, which shows that this strategy can avoid the distribution network congestion and ensure the frequency fluctuation of the system lower than 0.1 Hz.