As one of the main reason of fatigue failure, vibration has received more attention in reliability and comfort research on vehicles. The shock from bumpy roads has a great impact to the fatigue of vehicle parts and components. The method of survey user conditions is described for the road test in the article, and three accelerating data of X, Y, Z directions of a vehicle left shaft position have been obtained with the typical user condition. Through studied the data, we have obtained the load spectrum and the power spectral density data of one car. The obtained quantitative results from the analysis can be used for evaluating the comfort of using vehicle.