Abstract: As a concentration area of useful minerals, a mineral deposit is formed by geological processes and composed of some orebodies which are determined by geological exploration. Geological exploration is of stage characteristics. A certain exploration stage can only account for some orebodies of one mineral deposit or some sections of one orebody. Therefore, the determination of the resources and the boundary of a mineral deposit depends on the distribution of orebodies confirmed by more than one exploration event. Because the exploration stages of different exploration events in one mineral deposit are often different, the exploration stage needs reevaluation. This paper summarizes the principles of determining the boundary of a mineral deposit ,and puts forward the qualitative principles and a quantitative model for determining the exploration stage of a mineral deposit. These principles and the model not only can be successfully applied to determining the boundary of a mineral deposit as well as its exploration stage for The Quo-status Investigation of National Mineral Resources Utilization in China, but also can be used to determine the exploration stages of the mineral deposits in Equipped Exploration Areas. They are of realistic significance in reasonable exploration and exploitation of mineral deposits in Equipped Exploration Areas.