Many countries have been experienced a voltage collapse. The voltage collapse is mainly cause of imbalance between reactive power supply and demand. To overcome the imbalance in the electric power system, various voltage-var control devices have been used. To manage the devices efficiently, coordinated control those devices has been important. More efficient voltage-var control techniques in a power system have been proposed. To achieve a better control this paper presents a coordinated voltage control system with generators and switched shunt devices. Generators are equipped with automatic voltage regulator to maintain the voltage of generator bus. Switched shunt devices are installed on the network to control the voltage at each bus. Those devices have different characteristic time constant. Generators are much faster than shunt devices. When a disturbance in some power system network occurs, generators are more dominant factor in voltage stability. Power system operators have to control their system to have more reactive power reserve. In this paper a voltage control technique is to reserve reactive power of generators for emergency state in power system network through a coordinate control generators and switch shunt devices. These controls will be called CVC (Continuous Voltage Control) and DVC (Discrete Voltage Control) respectively. However, CVC has a different control scheme with AVRs in generators. It can control the voltage of a key bus in a power system network. The key bus has some characteristic such as reflects the change in all the voltage values of the network, has a sufficient reactive power reserve. In addition DVC control the reactive power reserve of generators to have more. Through coordinating two types of controllers the network has more reactive power reserve, could be controlled the voltages. Those coordinated control can make the network more stable with some disturbances. The study is presented by the Jeju power system in KEPCO (Korea Electric Power Corporation).