Abstract: In order to investigate the quantitative change law of rice pest population during the gradual changes of cultivation systems from double-cropping, the coexistence of single and double cropping to single-cropping, four monitoring points were designed to track and study the pest population structure and constitution number systematically between 1990 and 2012 using light trap and driving pests. The results were as follows: The number of pest species for rice was reduced to 8 from 9; The change law of pest population showed periodicity waveform curve change and the fluctuation cycles of W type and V type were 9-10 years and 4-5 years, respectively. While the fluctuation of different cultivation systems showed triangular change and the cultivation system of coexistence of single and double cropping was at a high operating model. Also, three mathematical models were constructed based on the numerical function simulation: Striped rice borer (F=-9.6459t2+158.54t+1920.9 (r=0.5648**)), Rice leaf folder (M=-636.37t2+22547t-162834 (r=0.7741**)), Rice hopper (N1=502.9t2-7097.8t+24522 (During 1990 and 2006: r=0.8050**) and N2=3122t2-133157t+1000000 (During 2006 and 2012: r=0.8191*). All these mathematical models would have an important guiding significance for single cropping rice pest monitoring and warning.