The invention relates to an operation control method of a double-fed wind generator participating in electric power system frequency modulation. The operation control method is characterized in that a deloading operation curve which has a power up-regulation capacity is set and a deloading control strategy in which variable speed and variable pitch are used for coordination control is designed according to an operation physical constraint condition of a Double-Fed Induction Generator (DFIG) which is common in a variable speed constant frequency generator, and the maximum deloading amplitude capability of the wind generator under each operation condition is quantitatively analyzed according to the operation physical constraint condition of the wind generator at different wind speeds. Through adjustment and control of a dropping frequency, the support effect of the wind generator to the system frequency under a deloading operation mode is verified. Through the simulation analysis, it is verified that in the deloading frequency modulation control scheme, when the system frequency fluctuates, the variable speed and variable pitch wind generator can effectively release kinetic energy, and the frequency support is provided for the system.