To address the issues of an unclear system frequency response model with a doubly-fed induction generator (DFIG) and insufficient utilization of rotor effective rotational kinetic energy, this paper proposes a frequency support strategy based on the effective rotational kinetic energy of the DFIG. Firstly, a system frequency response model including DFIG frequency regulation is established based on the traditional system frequency response model, and an expression for system frequency deviation considering wind power penetration is derived. The impact of DFIG frequency regulation on system frequency response characteristics with different damping ratios is analyzed. Secondly, the advantages and disadvantages of existing frequency support strategies considering DFIG rotor speed are deeply analyzed. Combining the regulatory requirements for frequency regulation control parameters of wind turbines in China, an adaptive frequency support strategy based on the effective rotational kinetic energy of the DFIG is designed. Finally, based on the IEEE 14-bus power system model, the superior performance of the proposed strategy in fully releasing rotor kinetic energy for frequency regulation under different disturbances, wind speeds, and wind power penetration conditions is verified.