tTobacco bacterial wilt caused by Ralstonia solanacearum is one of the most serious diseases of tobacco inthe area of tobacco cultivation. As there is no effective control method for tobacco bacterial wilt diseases,developing new antibacterial agents in tobacco will make great practical sense. The antibacterial activityagainst R. solanacearum of Lansiumamide B which is isolated from the seeds of Clausena lansium is reportedin this paper for the first time. The bioassay results indicate that Lansiumamide B could completely inhibitthe growth of R. solanacearum at the concentration of 125 mg/L in vitro, the EC50and EC90are 48.82 mg/Land 86.26 mg/L, respectively. The result of pot experiments indicates that the control efficiency of theLansiumamide B on tobacco bacterial wilt are 95.84%, 91.67% and 86.38% at 7 days, 14 days and 21 daysafter treatment at the concentration of 100 mg/kg, respectively, nearly 40 times higher than Streptomycin,a special fungicide to the disease, at 21 days after treatment with root irrigation method. These resultssuggest that Lansiumamide B has the potential of developing as a new type of plant-type fungicide oncontrolling the diseases of tobacco bacterial wilt.