Hierarchical and partitioned means of present voltage control results in the coordination problem among multiple coupling zones. From the perspective of game theory, split zones are regarded as game players in order to develop an individual rationality based cooperative game model, in which players search efficient alliance to improve their control effect. Players in the same alliance have a common optimization goal, while alliances play a noncooperative game, and the Nash equilibrium strategy would allow secondary voltage control area to consider the interaction and coupling from others thus avoid voltage oscillation and overshoot. A solution for nontransferable utility cooperative game is proposed, the existence of Nash equilibrium in the sub-problem is proved as well. Furthermore, steady-state simulation on IEEE 39-bus system demonstrates that the cooperative game model can effectively coordinate reactive power sources, thus improve the technical specifications of secondary voltage control.