In the Spatial Decision Support tool System （ISAT）

rules of expert system are expanded so that the expert system can not only use data extracted from GIS and database

but also need decision support models. By using these broad sense rules

we can bring knowledge process in geographic analysis

and integrate GIS

database and spatial analysis model. Model Data Blackboard is the key of integration

which consists of a variable table

a model table a true value maintaining system and a blackboard monitor. By this approach we can incorporate mathe models one by one. The system is also based on fuzzy logic. Model Data Blackboard can manage precision data and fuzzy data

and the mathe model functions exchange data between them through the model data blackboard. By prescribing the principle about computing certainty factors

certainty is processed approximately.\;Throught its knowledge macro language

the ISAT can setup a working environment for one spatial decision support course. The knowledge macro language program sets the objective of reasoning machine of the expert system

manages the input and output of the ISAT data. ISAT can interact with raster file of geographic information system

database and text file with its knowledge macro language program.\;The method introduced in this paper is also a preliminary way to design the knowledge based spatial analysis information system. We have done a case study with knowledge based investment assessment information system for urban district of Chongqing City in Sichuan province of China.