Electric vehicle will come into wide use in worldwide with the arrival of the Low-carbon society in the next twenty years. And total capacity of the battery on the electric vehicle in the power system network amounts for several Giga Watts, which corresponds to the capacity of several nuclear power plants. It is difficult for power system operator to forecast of the amount of the charging power because there is much uncertainty of using power on electric vehicles compared to the electric facility like air conditioner and so on. In order to operate the power system network stable, it is necessary for power system operator to control charging power of electric vehicle independently as controllable facilities.We propose a “Smart Charging” concept based on the index for the security monitoring of power system network which makes power system operation more efficiently and makes electric vehicle owners more conveniently. A load dispatch system, like distribution energy management systems or community energy management systems can take care of the voltage control considering the charging schedule of the electric vehicle's owner in advance and the result of power system state estimation or load flow calculation.In this paper, based on the hypothesis of spreading electric vehicle in a power system, a evaluation of charging that the electric vehicles starts simultaneously in the evening, a system structure of smart charging on electric vehicle based on voltage stability evaluation of power system, which distributes the charging power with more stable, and the test results of the smart power with the IEEJ standard data are explained.