Abstract: Adopting small plot experiment in the field, an efficacy of killing miscellaneous weeds by applying 41% Yibingcao-you in summer Pennisetum field were studied. The results showed that 41% Yibingcao-you were very effective to prevent and exterminate misecellaneous weeds in Pennisetum Field, but a little disadvantage to the growth of Pennisetum. In considering the ration of both the cost decreased and the grass safety, it is the best way to prevent and exterminate miscellaneous weeds that spraying 41% Yibingcao-you of 2.250L/hm2 diluted with water evenly over the field in 6 days after grass seeds sowed.