[Objective] The effects of runoff and sediment reduction by orchard grass cultivation in Northeast Guangxi Zhuang Autonomous Region was studied, in order to provide scientific reference for the development of soil and water conservation in this area.[Methods] Under the condition of natural rainfall, the runoff and sediment data of Paspalum thunbergii and Ageratum conyzoides were compared and analyzed in different slopes (i.e. 12°, 23°, 42°).[Results] ① When the slope was 12°, rainfall had a significant effect on runoff and sediment yield of Paspalum thunbergii and Ageratum conyzoides (p<0.05). ② Under the same life cultivation, the runoff and sediment yield increased with the increase of slope gradient. Compared with the clear cultivation, the runoff and sediment yield of Paspalum thunbergii decreased by 33.06%~50.35% and 67.09%~77%, respectively, while that of Ageratum conyzoides decreased by 21.89%~28.85% and 41.65%~47%, respectively. The runoff and sediment reduction effect of Paspalum thunbergii was better than that of Ageratum conyzoides. ③ The interaction effects of slope and grass cultivation were significant on runoff and sediment yield (p<0.001). With the increase of slope, the effects of grass cultivation on runoff and sediment yield on slope were gradually weakened, while the effect of slope was gradually enhanced. Nevertheless, the effect of Paspalum thunbergii cultivation on slope sediment yield was always greater than that of the slope.[Conclusion] The runoff and sediment reduction effect of Paspalum thunbergii was better than that of Ageratum conyzoides in the same slope. The effect of grass cultivation on runoff and sediment production on slope decreased with the increase of slope, while the effect of slope increased gradually. The effect of Paspalum thunbergii on slope sediment yield was always greater than slope.