Excessive voltage fluctuation has been a problem existing and to be solved at grid connected point of wind farm, on which, the paper develops the study by taking the double-fed wind farm as an example. First, it studies and deduces the DFIG model and the equation for voltage of grid connected points of double-fed wind farm and analyzes the vector control strategy of DFIG gird-connected system in theory. Based on this, it puts forward to an improved adaptive voltage control strategy of double-fed wind farm. Finally, it conducts the simulation of grid-connected system of double-fed wind farm with DIgSILENT simulation platform under the premise of fluctuating wind speed. Simulation results indicate that improved adaptive voltage control strategy is able to maintain constant and smooth voltage at grid-connect points of wind farm. Thus, the control strategy is able to effectively suppress voltage fluctuation at grid-connect points of wind farm and maintain the bus voltage as the target value so as to integrate wind energy into the grid at maximum efficiency.