Combined with the historical data,the factors causing the outbreak of brown planthopper( BPH),Nilaparvata lugens( Stl) were analyzed by the method of ecological principle of insect population in Fujian in 2015. The results revealed that the mixture of immigrants amd local initial populations were the important incentive causes of outbreak of BPH,but the key and crucial cause of internal was the extremely high growth rate of BPH. And the favorable weather conditions corresponded with the rice period of head...