Road erosion is one of soil erosion types in regions. To grasp the mechanism of road erosion, runoff plots were used to make observations, and results show that :(1)Characters of rains in study area: the rainfall and rain intensity are mainly 5~10 mm and <5 mm/h respectively in most rain events, and they brought 52.89 mm and 61.31 mm rainfall respectively, which getting to 56.72%,65.76% of whole rainfall respectively.(2)There are well linear relationships between the product of rainfall and rain intensity,sediment concentration and runoff depth, and their correlation coefficient are 0.657 6 and 0.798 2 respectively. These are well accordance to USLE, so the integration of rainfall and rainfall intensity can be an important factor to predict soil losses from road embankment slope. (3) Natural logarithms of sediment concentration and that of runoff depth are well linear (correlation coefficient R=0.863 3), sediment concentration is increased with runoff depth increasing.Mean runoff coefficients is 0.29, of which show that there are large infiltration capacity in the embankment slope.