The susceptance calculation of compensation has important influence on the compensation performance of static var compensator when it is used for load compensation.A new susceptance calculation method of SVC based on synchronous symmetrical component is proposed in this paper.A single-phase voltage is derived and used to form the virtual symmetrical three-phase system.The axis of the synchronous reference frame is always synchronous with the voltage vector in virtual symmetrical three-phase system.Then the load current is projected on the voltage vector.The components of positive and negative sequence load current

which is feed into low pass filter

are obtained

and the compensation susceptance is therefore calculated accurately.This method is simple in calculation

and the SVC based on the method without phase locked loop（PLL） of hardware can compensate reactive power accurately and keep voltage stable quickly.The feasibility and effectiveness of the susceptance calculation method is verified by simulation and experimental results.