The more knowledge the expert system has, and the stronger its ability to resolve problems will be. For a long period of time, the knowledge of the expert system commonly came from humen experts. However, there may probably exist a "blank" of knowledge in experts' experience. If the knowledge from theoretical analysis and data from case histories of engineering works are added to the knowledge repository, the knowledge capacity of the system will be increased.There are different hydrogeological problems for different types of mines, and these problems cannot be resolved only by relying on experts' experience. On the other hand, the available hydrogeological data in a mine are a valuable wealth, which can be exploited and utilized. The system's ability of resolving problems will be raised greatly when drawing the experience of mine hydrogeologists and hydrogeological workers, relevant contents of rules and specifications in operation and other results of theoretical analysis and data from the operations of numerous mines as the knowledge source of the system.The establishment of an inference frame and better application of knowledge and information are of vital importance for the second kind of expert system. The nonferrous metal mine hydrogeological evaluation expert system (MHGEES) is developed with the passage ways of groundwater migration as the trunks of the physical model, the transformation of different kinds of water and changes of hydrogeological conditions as the core of the analysis model and the knowledge application techniques such as the analysis based on levels and analogy analysis made in four steps to construct the facts and rules.Based on the data of investigations of eighteen nonferrous metal mines and the practice of constructing the MHGEES system. The author expounds the characteristics of two different expert systems and discusses the techniques of constructing the second kind of, expert system.