Abstract: The determination of cut-off grade must take into account the dynamic characteristics of grade in time and space and the randomness of grade distribution.Taken into account the spatial and temporal characteristics in mining of the ore body, a new cut-off optimization model using stochastic programming to maximum the net present value function of a mineral enterprise was formulated, the randomness and uncertainty of grade distribution in different section, and production capacity of a mineral enterprise in an open-pit mine.So the optimized cut-off grade is the best indication of the real operation situation of a mining enterprise.

Key words: Cut-off grade, Optimization, Stochastic programming, Open-pit mine, Net present value