In order to analyze voltage stability in large-scale wind farms integration area, this paper proposes that dynamic reactive power control should be considered. Presently, dynamic reactive power compensation device in wind farms widely adopts constant reactive power control. According to it, this paper firstly proposes this control mode of dynamic reactive power compensation device can bring voltage stability problem based on voltage-reactive power sensitivity method; then it uses small signal stability analysis method, consulting that there is a strong interaction between dynamic reactive power compensation devices in wind farms which adopts high-voltage side constant voltage control. As a result, it will lead to unstable high frequency oscillation; finally, taking a wind farm integration area in North China, it obtains the voltage change of all dynamic reactive power compensation device in wind farm after small disturbance when constant control mode, high-voltage side constant voltage control, and low-voltage side constant voltage control are adopted respectively. The result shows that considering dynamic reactive power control is important for voltage stability analysis in large-scale wind farms integration area.