The effects of vegetation type, rainfall intensity, surface crust, and weed cover on rainfall infiltration and runoff on grassland and bare land were studied under simulated rainfall conditions. The results show that surface crust could easily take place on bare land, so its runoff-yielding time primarily depends on rainfall intensity, and their relationship might be described by a power function. However, runoff-yielding time on grassland with a higher cover ratio primarily depends on initial soil water content, and their relationship might be described by a linear function. Compared with bare land, grassland could delay and intercept runoff effectively. After surface curst was formed on bare land, runoff generation would be earlier and the average infiltration rate would be lower. However, bare land covered with weed, especially in the middle and bottom parts of the hillslope, would delay and intercept runoff, increase infiltrated water, and make soil water move deeper. Moreover, evaporation inhibition after rainfall also has the similar effects.