The filter hardware structure design of traditional back EMF method will lead to the commutation error of the position sensorless brushless DC motor. When the commutation error is large, the performance index of the system will be greatly reduced. Aiming at the problems of system commutation torque ripple and outofstep caused by commutation error, the relationship between the ideal backEMF zerocrossing point and the actual backEMF zerocrossing point is analyzed; on the base of adding a singleended primary inductor converter (SEPIC) predriver circuit, this paper adopts PWMONPWM modulation method, which detects and compares the voltage value of the nonconducting phase (i.e., the suspended phase) and the calibrated voltage value, then a commutation signal is obtained and the commutation error correction is realized. Compared with the traditional backEMF method, the proposed method needs only to detect one phase voltage, then the commutation error is accurately corrected and the torque ripple of the system is reduced at the same time. Simulation and experiment results verify the effectiveness of the proposed commutation error correction strategy in full speed range.