The friction of rolling bearing is produced by many factors in a complex system.In order to study the proportion of the friction of various friction pairs in the total friction of bearings,taking the 6204 grease lubricated deep groove ball bearings commonly used in idles of mine belt conveyor as an example,the main sources of friction resistance of grease lubricated deep groove ball bearings were analyzed,and the bearing friction was divided into rolling friction,sliding friction,viscous friction and sealing friction.The friction experiments were carried out under sealed,unsealed,unlubricated and micro-lubricated conditions of the same batch of 6204 grease lubricated deep groove ball bearings,and the influence of each friction component on the total friction was analyzed by peeling off some factors successively.The experimental results shows that under the conditions of experimental loads and speeds,the sealing friction accounts for about 5% to 18% of the total friction of the bearing,and the viscous friction accounts for 64% to 85% of the total friction of the unsealed bearing.In addition to these viscous frictions,the sliding friction is also an important component of the total friction of the rolling bearing.