Abstract: The torque response of interior permanent magnet synchronous machines (IPMSM) is investigated according to the torque response demand of driving motor in hybrid electric vehicle(HEV) application. To meet the demand, a flux weakening strategy combined with over-modulation strategy is proposed. The proposed strategy is verified by simulations and experiments, which indicates that torque responses much faster under the condition of the modulation index greater than the max linear modulation index. In addition,the comparison between the proposed strategy and traditional flux weakening strategy which based on output voltage closed-loop control is also studied. The results show that proposed strategy can fulfill the demand in HEV application.