The mechanical and electrical systems are decoupled and controlled in doubly fed induction generator（DFIG） using double PWM converters. That leads to poor responding performance of DFIG wind turbines generator to the change of the power system frequency. According to its characteristic and scheme， a frequency control loop based on the model of DFIG based wind turbines is proposed and it is implemented in the simulation package of DIgSILENT/PowerFactory. During the deviation of power system frequency， the DFIG based wind turbine with frequency control loop can release（or absorb） a part of the kinetic energy stored in rotor， so as to increase（or decrease） active power injected to power system to realized the frequency control. Validity and practicability are verified by simulation. It lays a foundation for wind farm participating system frequency regulation.