The digital deposit model is meant to transfer the deposit features described in traditional geological terms into the data and code that can be understood by computer and put AI knowledge and rules into computer so that the computer can reasoning automatically and assist geologists ,exploration companies to make decisions. The research is based on the achievement of the predecessors, combined with advanced theory and experience from domestic and abroad .The paper set forth the principle and method of digital copper deposit model and some key techniques in the implementation of the system. The knowledge and rules were built with the help of the copper geologists, who provided the parameters related to the reasoning such as pre probabilities, which were handled with statistics method. The database development skills were applied to store and manage the knowledge and the rules while the knowledge founding adopted data mining technology. The system use the production rules and adopt subjective Bays method as the algorism The search strategy is span priority and forward search. Different from the previous system which provided limited evidence only directly related with the copper deposit, the abundant evidence is offered for users to choose ,which lead to more reasonable and reliable conclusion .Moreover ,it has the function of geological dictionary ,which make the users more convenient to query and search. The system can not only infer solitary cause deposit, but also predict the complex causes deposit. The result presented in this paper reflect preliminary achievement of the project supported by Chinese High-Technology Research and Development(863) Program.