Brushless DC motor (BLDCM) has the question of torque ripple and it will influence the motor's running stability. The theory of commutation torque ripple of BLDCM was analyzed firstly. After the study of the stop process of BLDCM, it was proposed that the motorpsilas stop precision will be affected when commutation occurs in the stop interval. Classical overlapping commutation and novel dynamic commutation technique are both used to solve this question separated. Through theoretical analysis and the experimental results, it was found that the bus current was smooth at any time when dynamic commutation technique was used. So the torque ripple was reduced and the stop precision was improved obviously.