A rolling forecasting model of wheat scab was set up using CBR theory with time series. To improve the accuracy and reliability of this model, impact factors and parameters, such as model unit, prediction stages, meteorological factors and its weight were optimized by using the database system of crops pests in Anhui province and the results of expert consultation. The accuracy of CBR model of wheat scab with optimized parameters was tested, and the results showed that the precision rate was 84.21% in a normal year. The optimized factors and parameters could be applied to the forecasting model of wheat scab.