Abstract: The open winding brushless DC motor has no neutral point, and the phase windings are electrically isolated, which can realize independent control of each phase. Firstly, the mathematical model of open winding brushless DC motor is introduced, the influence of each phase caused by the mutual inductance and the impact of the diode freewheeling for non-commutation phase with the same bus power supply are analyzed. Secondly, the current commutation process of open winding brushless DC motor during the commutation period is analyzed. It is concluded that if the turn-off and the conduction phase current with the same change rate, under the ideal Back EMF condition, the non-commutation phase current is constant, then the electromagnetic torque remains the same. Thirdly, the working principle and process of overlapping commutation with phase current closed-loop control are given, the voltage applied on turn-off phase and delay shutdown time formulas in overlapping commutation are derived, electromagnetic torque is calculated by the Back EMF which is observed by sliding mode observer. Finally, the method of overlapping commutation with phase current closed-loop control are carried on the Matlab simulation analysis, the experimental results indicate that the control method can realize the commutation torque ripple suppression of open winding brushless DC motor.