By analyzing the functions of the static var compensator (SVC) applied to extra high voltage (EHV) AC power transmission, the control strategy of SVC is proposed. This strategy takes system voltage (e.g. 500 kV) as the main control objective to achieve stable voltage, increase power transmission capacity, promote voltage recovery after the failure, and depress oscillation etc. In view of the high capacity of each SVC in the EHV power grid, the measures are proposed to prevent the valve manifolds and the total circuit breaker over-current, and the voltage busbar over-voltage in the control process.