Based on the pentadbypentad data of systematic investigation of riceplanthopper population per 100 crowds from 2005 to 2007 at Tongcheng, the main meteorological factors affecting the occurrence grade of riceplanthopper have been analyzed. The results show that: there are significant negative correlations between dekad average temperature, pentad average temperature and the data of riceplanthopper population per 100 crowds, high temperatures have inhibition effects on riceplanthopper population, and the optimum pentad average temperatures for occurrence of riceplanthoppers are 20.5 ℃. The model of forecasting riceplanthopper occurrence by use of Kalman filter has been established, which can forecast the meteorological conditions of riceplanthopper occurrence and provide a basis for pest control. The historical data fitting and test application in 2008 show that the accuracy, reliability and stability of the model are good, therefore it can be applied to agrometeorological operations.