Abstract: In order to realize efficient development to scarce geological resources,an economic evaluation model for mineral deposits is established by taking net present values (NPV) as the objective function.The method of profit element is introduced to calculate the equivalent grades.Then,based on the three-dimensional digital deposit model,an optimization algorithm for calculating both of the optimum comprehensive cut-off grade and the break-even cut-off grade is developed when respectively directing to the objectives of a maximized NPV and the zero NPV.A practical application of the model to calculating the optimized cut-off grades has been done through a copper-molybdenum deposit case.It is approved that it can not only provide accurate economic analysis for the mine investment and production planning,but also ensure the optimal utilization of resources.