Abstract: With the application and development of modern science,techniques,micro-and macro-sensors,the tremendous amounts of spatial and nonspatial data have been stored in large spatial databases.These are far begond the human ability to interprete and analyse them,which is badly in need of SDMKD to provide knowledges.This paper presents an overview on SDMKD.First the derivation and development of SDMKD are briefly stated.Second,the concept of SDMKD is discussed.There are various knowledge which can be mined from spatial databases or spatial data warehouse,e.g.spatial association rules,spatial characteristic patterns,spatial classification regularities,spatial clustering rules.Third,SDMDK is told from data mining and knowledge discovery (DMKD),machine learning,geographical data analysis,spatial databases,spatial data warehouse,digital earth,etc.Finally,how to develop SDMKD software is concluded and discussed.