Abstract: The management of crop diseases and insect pests was a complexity system.This paper introduced the basic models of grey system and the author gave the GM (1, 1) model of crop diseases and insect pests using the grey system.The verify precision of model simulating comes to first level, its expand modulus (a) was less than 0.3.So the model could be used as mediunrterm or long-term forecasting for crop diseases and insect pests.