An analysis is made the key areas of various weather systems affecting Anhui Province, based on the objective analysis of weather patterns by means of NCEP 500 hPa height and grided wind data, forecasters' experiences, and the conventional precipitation measurements of ten years in nonflood season from 81 stations over Anhui Province. The daytoday weather calendar resulted from automodeling is used in the weather modification forecast system, and objective typing of circulation patterns is realized. The method is practicable and highly automatic,can provide useful references for the control system of precipitation enhancement operation in Anhui.