The traditional reliability test scheme of the heavy vehicles is depended on the experience,which was lack of quantitative index of wear data of the vehicles.Through analyzing the wear elements concentration of oil spectroscopic analysis for vehicular power transmission system on different roads,the impact factors of different road surface on the wear reliability of vehicular power transmission system was determined.A new method was given to the reliability prediction of vehicular power transmission system based on oil grey theory of road impact factors.The wear life of vehicular power transmission system was predicted,and was compared with the actual test data,which validated the correctness of model.The reliable predication method based on oil grey theory of road surface impact factors can make a rational test scheme of the heavy vehicles based on quantitative index.