Abstract: Effect of defoliation frequency on the growing characteristics and yield of Pennisetum americanum譖.purpureum were studied under the condition of middle soil fertility and two fertilization rates.The results showed that the annual biomass amounts in the treatments of 30 d,45 d and 60 d defoliation interval were 193.48 t·hm-2,269.75 t·hm-2 and 237.77 t·hm-2 respectively.Defoliation stimulated the tillering trend of Pennisetum americanum譖.purpureum,however,frequent defoliation (30 d) reduced the up-ground biomass,caused the exhaustion of root system.Defoliation in long-term recycle (60 d) resulted in a reduction of biomass production,an increase of stem/leaf ratio.The biomass and growing characteristics of Pennisetum americanum譖.purpureum in the treatment of 45 d defoliation interval were more ideal for its husbandry utilization of grass-eating animals.