Abstract: The selection of cut-off draw-grade is closely related to the resource reco-vory, profit and annual output of concentrate, thus it is concerned with the-composite, technical-economic effect. This paper is only to discuss emphatically one of them, that is the profit index.
This paper suggests three knids of profit index to evaluate the economic effect, they are:1) the profit per ton of the write off recoverable reserve; 2) the profit per ton of recovered orc; 3) profit-cost ratio. The relationship between marginal benefit and mean profit is analyzed from the point of view of marginal benefit, so that the criteria of maximum value of the above mentioned profit indexes can be deduced respectively. To use these criteria and the two break-oven points, the draw process can be divided into severed section and each of them has diffeient benefit leved, which provide economical bisis for final dcsision of cut-off draw-grade.