ELM (Extreme Learning Machine) is easy to use. It has fast learning speed and good generalization. This paper researches pests forecast based on ELM. In order to improve the efficiency and accuracy of ELM ,this paper uses ELM to pretreat all samples and then traines, forecasts the processed data as the input data of the ELM.Simulation Experimental results show that ELM has high accuracy and good generalization which meets the requirements about accuracy and real-time. This paper supplies a new method to forecast pests according to the instance.