Abstract: The 5 MW wind turbine is the research subject and the life model of the transmission system coupling the gearbox is established in this paper.Basing on the ISO281:2007 standard and Palmgren-Miner linear cumulative rule,the effects of the error on the loading and the fatigue life of the planetary bearing under the random wind load has been discussed.The results indicate that the planetary pin position error in the radial direction have less effect on the loading and the fatigue life of the bearing.The error in the tangential direction take great effects on them.The loading distribution of the up-wind bearing and the down-wind bearing can be changed under the planetary pin position error in the tangential direction.The effect of the planetary pin position error on the load and the fatigue life of the down-wind bearing is large.