To solve the dc drift and integral saturation phenomenon produce the error of the vector orientation problems in the traditional virtual flux observer, the virtual flux observer consisted of the low-pass filter and high-pass filter is designed. The observer instead of power grid voltage sensor in three-phase grid-connected inverter, can effectively reduce the harmonic distortion and the cost control system. The simulation was taken on the observer and showed that the observer can eliminate integral saturation phenomenon and the influence of the dc component on the positioning accuracy, and improve the dynamic performance of the system. The virtual resistance method combine with inverter can improve the performance of the LCL filter, and achieve unity power factor operation.