Abstract: To restrain the terminal high voltage of DFIG（doubly fed induction generator） after occurring low voltage ride through（LVRT） which can cause the ’second-time tripping’,the reactive power control principle of DFIG with constant voltage mode of converter at the rotor side is analyzed.It’s pointed out that the reactive power adjustment of DFIG during LVRT can lead to terminal high voltage during the low voltage period.Based on the simplified mathematical model,the approximate expressions of terminal high voltage amplitude and its key affecting factors are given.Then,an improved constant voltage control method of DFIG is put forward to restrain the terminal high voltage after occurring LVRT.In the end,the grid-connected DFIG model is built by MATLAB/Simulink,and simulation results verify the validity of the theoretical analysis and the effectiveness of the proposed constant voltage control method.