The transmission efficiency of driving axle directly affects the vehicle fuel consumption,and the difference of driving axle bearing clearance affects transmission efficiency. On the basis of the theory research,it is found that,by benchmarking analysis and further experimental research,through increasing the bearing clearance,the transmission efficiency of driving axle can be improved,and the vehicle fuel consumption is decreased. Meanwhile,through increasing the bearing clearance,the life mileage of the bearing is reduced and the noise of driving axle is increased. Considering minimizing the user cost,the proper increasing of bearing clearance has great important significance on improving the transmission performance of driving axle.