Road erosion in the loess region is a severe problem which influences traffic,transportation and agricultural activities etc.Research on road erosion is very important to soil and w ater conservation,ecology construction and economy development in the region.Based on simulated rainfall experiments,erosion processes on loess roads are studied,and following results are obtained.(1)The variations of starting time of soil erosion by runoff with rainfall intensity and slope gradient can be respectively described with exponential equations.(2)The sediment concent ration is very high in the initial stage of soil erosion processes by runoffon road.However,the concent ration decreases very quickly,and then gradually becomes relative steady in continued rainfall processes.(3)The variation of road erosion rate can be divided into three stages during which the variation of erosion rate with rainfall process is great from the commence of soil erosion by runoff to 20min,and from 40min to the end of runoff erosion processes,and is relatively steady from 20min to 40min.(4)The variations of road erosion modulus with rainfall intensity and slope gradient can be described with exponential equations,respectively,and the integrated effects of rainfall intensity and slope gradient on road erosion can be described with a binary linear equation.