An automatic voltage coordinated control system by coordination between provincial and district power networks is designed and implemented. The automatic coordinated control mode is designed based on bidirectional-interaction. A coordinated control agent is introduced， and the multi-agent system coordination structure is proposed. The reactive power and voltage on the provincial and district boundary are chosen as coordinated variables. The provincial agent provides the voltage ability constraints and reactive power demand constraints， while the district agent provides the voltage demand constraints and reactive power ability constraints. With these coordinated constraints， the coordinated control agent generates a coordinated control strategy for the provincial and district agents. The coordinated control system has been implemented in Jiangsu power grid and an excellent performance has been observed.