With the large penetration of renewable energy, fulfilling the balance between electricity demand and supply is a challenge to the modern power system. According to the UK government, the wind power penetration will reach 30% by the year 2020. The role of electric vehicles (EVs) contributing to frequency response was investigated. A dynamic frequency control strategy which considers the comfort level of vehicle owners was developed for EVs to regulate their power consumption according to the deviation of system frequency. A simulation model of a population of EVs equipped with such control was implemented in Matlab/Simulink platform. In this paper, a simplified Great Britain power system model is used to study the contribution of EVs to dynamic frequency control. The case study showed that using EVs as a demand response resource can greatly reduce the frequency deviations. And the rapid response from EVs can help reduce the operation cost of conventional generators.