Using MICAPS realtime sounding data, the atmospheric inversion layers of single stations were converted into atmospheric horizontal inversion zone and the automatic diagnostic analysis of the latter was achieved， by researching the relationship of atmospheric horizontal inversion zone and freezing rain falling zone. Afterwards, the atmospheric horizontal inversion zone, highaltitude wet areas, the ground air 0 ℃ line, and the 0 ℃ line of extreme temperature of inversion layer, were used to constitute the basic conceptual model of freezing rain falling zone; furthermore, on the basic conceptual model, the automatic diagnostic analysis method of freezing rain falling zone was developed and was tested in the severely freezing weather in southern China early 2008. The method shows the strong diagnostic analysis ability and has good prospects for operational applications.