In order to assess the reactive power and voltage control capability of a wind farm, this paper builds a wind farm reactive power and voltage control double evaluation system, and introduces a quantitative classification method based on probability statistical indicators. Then, two subjective weights are obtained by a scale-extending analytic hierarchy process and precedence chart, and two objective weights are obtained by entropy weight and the coefficient of variation method. The weight is optimized by the combined weighting method aiming at the minimum deviation. The reactive power and voltage control capability of a real wind farm in Hunan Province is comprehensively evaluated. The effectiveness of the proposed evaluation method is verified. The evaluation results can reflect the overall situation of the reactive power and voltage control capability of the wind farm. In addition, the combined weights can take the advantage of subjective and objective weights into account. This work is supported by National Natural Science Foundation of China (No. 51822702) and Science and Technology Project of State Grid Hunan Electric Power Company Limited (No. 5216A5170011).