Abstract: Based on the average life table,by means of the population matrix model,the abort-term forecast of the population dynamics of brown rice planthopper,Nilaparvata bgugems(BPH) was studied in this paper.The BPH population was grouped in the life table,during the egg,1st-2nd instar of nymph,3rd-5th instar of nymph and adult stages.It was problem that the developmental rates in various stages were unequal.In this paper,the varias groups were subdivided into daily states to compose the state vectors and the transitional matrix is also expanded to square matrix correspondingly.The BPH numbers in daily stages would be outputted continuously fir 40 days (x (t1) to x (t4s)) by using the output mathematical model,when the state variables of the initial time (X (ts)) were inputted.The forecasting results from the output mathematical model may be realised in the similar conditons,if the rice variety resistance range to BPH and the other interference factors are not changed evidently.