The existing frequency control method of doubly-fed induction generators (DFIGs) is unable to fully use the rotor rotational energy to support the frequency and a secondary frequency drop is caused during the rotor speed recovery of the DFIG. To address these issues, this paper suggests a self-adaptive frequency control scheme of a DFIG with smooth rotor speed recovery. First, during the frequency support stage, the coupling relationship between the droop control coefficient of DFIGs and the frequency deviation is established using the exponential function so that the control coefficient becomes large with the increasing frequency deviation. DFIGs can release more rotational energy to the power grid and then improve the frequency nadir. Secondly, during the speed recovery stage, the control coefficient gradually decreases to zero within the preset period by using the first-order decreasing function so as to achieve controllable rotor speed recovery and remove the secondary frequency drop. Finally, an IEEE 4-machine 2-area power system model is modeled using an EMTP-RV simulation to illustrate the effectiveness of the proposed frequency control scheme. This work is supported by the National Natural Science Foundation of China (No. 51877112).