Three-phase voltage and power flow can be given and load side neutral point voltage offset cannot be measured in the substation, but establish and solve the three-phase power supply current mathematical model in the premise must be known neutral point voltage offset. Come up a balance compensation method to measurement the neutral point voltage offset. Use under the condition of asymmetrical three-phase current. On the basis of the neutral point voltage of zero corresponds to obtain the asymmetric load. Then, a parallel compensator is used to compensate for the unbalanced load. By asymmetric load and compensation reactance of star delta transformation of asymmetric load is modified, and then on the basis of compensation of asymmetric current is equal to the load current conditions are repeated iteratively calculated accurately calculate unsymmetrical load and the neutral point voltage offset is obtained. In this way, the system power factor is compensated. Based on the case of a substation in Guangdong, the correctness of the method is proved by Matlab simulation.