This paper proposes a control method with control frequency asynchronous to Pulse Width Modulation (PWM) frequency for Vienna rectifier to enhance the stability when connected to the grid. By analyzing the bode diagram of the current control system of the Vienna rectifier, it is revealed that utilizing the converter-side current as the control object is more stable than grid-side current. Further, the digital control delay leading to instability in some cases for traditional current control utilizing the converter-side current as the control object is evaluated by using phase portraits. To deal with this issue, the control frequency is designed multiple times of the PWM frequency to eliminate the control delay as possible as it can be. Lastly, the effectiveness of the proposed method is validated by the simulation results.