Abstract: PQ control is generally used to regulate active and reactive power of grid-connected converters. However, traditional PQ control based on PI has difficulty in determining control parameters and is mal-adapted to uncertain model parameters. Consequently, we put forward an improved PQ control algorithm for the grid-connected converter under current vector orientation based on backstepping control. And an approach for the determination of the control parameters in backstepping control is designed in consideration of the control performance. Firstly, the grid current vector oriented coordinate system is constructed and the space vector model of the grid-connected converter under the coordinate system is established. The controllers of grid-connected current and power factor angle based on backstepping control are designed and their stabilities are proved theoretically. Then, the uncertainty of model parameters is taken into account and the transfer function and steady-state error in control links are integrated, and the control parameters in the controllers are determined according to the requirement of control performance to further optimize the control performance on the basis of satisfying the stability. Finally, both simulation and experiments are conducted to verify the control approach. The results show that the improved PQ control algorithm can significantly improve the speed and accuracy of the grid-connected converter to track power reference signal, and the designed backstepping control parameters are negligibly affected by the disturbance in system model parameters; thus the operating performance of the grid-connected converter is effectively improved.