Brushless dc motor (BLDCM) commutation torque ripple when is always the concern, but the present is limited to 120°conducting way of research, this paper studies the 180°conduction mode brushless dc motor in the commutation torque ripple during the period of change, and with 120°conduction mode torque pulsation were compared. The results show that, the motor in the low speed region, 120°conduction ways than 180°conduction mode torque ripple changes little, and in high speed region, 180°conduction ways than 120°conduction mode torque ripple changes small. The analysis results for brushless dc motor new torque suppression strategies to provide a theoretical basis.