The invention discloses a sensitivity-based reactive power regulation priority selection method of wind farms. The method mainly comprises the step of solving the sensitivity between grid connection point voltage of one wind farm and output reactive power of the adjacent wind farm through reactive power-voltage sensitivity matrixes and a node power balance equation, thereby obtaining a priority sequence of actions of the wind farms for large-scale on-site reactive power voltage regulation and mutual compensation. Therefore, the problems of on-site reactive power control disorder, delay and the like of a wind farm group in the prior art can be solved.