In this paper, we propose a new decentralized multi-agent approach for a voltage control using LRT transformers and static condensers (SCs)/shunt reactors (SHR). The proposed multi-agent system is constructed with two-Ievel hierarchical architecture. Several Local Area Control Agents (LAGs), which correspond to the local area control system, are located at the sub-stations/power-stations in the lower voltage level areas, while Several Global Area Control Agents (GAGs), which correspond to the global area control system, are located at the substations in the high voltage level areas. In order to demonstrate the capability of the proposed multi-agent system, it has been applied to a model power system network. The simulation results show that the proposed multi-agent approach is effective and promising.