Abstract: The connection of large-scale renewable energy to the power grid reduces the frequency stability of the power system, which brings new problems and challenges to the secondary frequency regulation of the power system. With a large cluster, the electric vehicles have become a new type of frequency-regulation resources due to its accurate and fast dynamic response capability. This paper first summarizes the system framework of numerous electric vehicles participating in frequency-regulation ancillary service and introduces two methods to quantify the adjustable capacity of aggregated electric vehicles. One method quantifies the adjustable capacity of the aggregated electric vehicles directly, and another one presents the energy feasible region of the aggregated electric vehicles. Then, the day-ahead optimal scheduling and the real-time control process of electric vehicles participating in secondary frequency regulation of the power system are reviewed from different aspects: model, method, and application. Finally, the future research direction and key technologies of numerous electric vehicles participating in secondary frequency regulation of the power system are prospected.