Through indoor simulated rainfall experiment, three kinds of rainy intensity (30, 60 and 90 mm/h) and three types of slope cover (bare slope, 1 cm Masson's pine litter cover, and 1 cm Masson's pine ash cover) were set up to study the process of runoff and sediment yield of slope under different ground cover before and after forest fire, and to clarify the benefits of runoff and sediment reduction under pre-fire litter cover and post-fire ash cover. The results showed that: (1) Compared with the bare slope, the initial runoff yield time was extended by 33%~80% and 51%~200% on litter-covered slope and ash-covered slope, respectively, and the ash cover had a more obvious ability in delaying runoff generation. (2) Compared with the bare slope, the runoff reduction benefit of litter cover was stable at 12%~36% under three rain intensities, while the runoff reduction benefit of ash cover was larger than 70% under 30 mm/h and 60 mm/h rain intensities, and reduced to 7% when the rain intensity was 90 mm/h. (3) The runoff yield on the bare slope showed a trend of rapid increase at first and then stable, while on the slope covered by litter and ash exhibited "stepwise" upward trend. (4) Litter cover could reduce runoff sediment carrying capacity and total sediment yield, and the sediment reduction benefits were all over 85% under the three rain intensities, and higher than that of the ash-covered slope under the same rainfall intensity. The runoff and sediment reduction benefits of the litter cover were relatively stable under different rainfall intensities, and the runoff and sediment reduction benefit of the ash cover was significantly affected by rainfall intensity. Moreover, the sediment reduction benefits of the litter cover was superior to the ash cover under three rain intensities, indicating that the change of land cover after forest fire was one of the critical factors causing the increase of soil erosion.