Abstract: The reason why the Neutral Point (NP) voltage unbalance is analyzed in detail,and a Fuzzy Controller based on control index proposed. Fuzzy controller can automatically and intelligently find the value of the control index and adjust the operation time duration of the small vectors. This method for balancing the NP voltage is simple and need not extra hardware cost. In the study, the design method of fuzzy controller has also been presented in details. Finally, the experimental results verify the proposed technique and the balance of the NP voltage guarantees high power factor of TL-PWM rectifier.