The grasshopper infested again in Inner Mongolia grassland in 2004. The higher temperature in the winter and in the spring and the precipitation in the earlier 10 days in May,2004 are favorable to the incubation of the grasshoppers. The appearance date is 11 days ahead of time. Drought and desertification are the two main climatic factors that lead to the grasshopper infestation in succession since 2000.