The invention relates to a system and a method for controlling low voltage ride through of a double-feed induction wind driven generator in power grid voltage instantaneous drop. The system comprises a double-feed induction wind driven generator and a rotor excitation converter which consists of a rotor side converter and a grid side converter, a voltage Hall sensor is arranged on a synchronization common coupling joint, a rotor winding terminal of the double-feed induction wind driven generator is provided with a current Hall sensor, and a digital signal processor is connected with the rotorexcitation converter, the voltage Hall sensor and the current Hall sensor. The method comprises the steps of: detecting rotator current and carrying out synchronous rotation coordinate transformation; filtering induced current generated by stator flux linkage direct current components and negative sequence components on a rotor in the power grid voltage instantaneous drop; inversely adding into rotor current given values; generating a magnetic field opposite to the stator flux linkage direct current components and the negative sequence components in the rotor; rapidly weakening the stator flux linkage direct current components and the negative sequence components; reducing the influence of the stator flux linkage direct current components and the negative sequence components on a rotor side; and finally achieving the purpose of reducing the stator flux linkage direct current components and the negative sequence components. A hardware protection circuit is not additionally arranged in the control method; and the system has simple structure and high reliability.