The Soil Taxonomy offers a theoretic basis for establishment of a soil classification expert system(SCES),which divides soil types according to quantitative soil indexes.The Geographical Information System(GIS) technology offers an effective tool for automatic mapping of soil classification.This paper concentrates on reasonable methods of developing SCES and automatic soil mapping by simulating thinking processes of soil classification experts and using the GIS technology.Firstly,objectoriented methods are used to express the experience and knowledge of soil diagnostic horizons and diagnostic characteristics of soil classification experts;and on such a basis,decision tree structures and consequence ways are discussed.Then a logic structure of the SCES,methods to combine geographic information with automatic soil classification,and the framework of an automatic soil classification searching system based on GIS and ES are brought forth from the angle of knowledge expression of soil classification experts and construction of an inference engine.