Abstract: This paper deals with the methods to outline ore bodies and to block-out different reserves/resources under the condition of the Chinese market-oriented economy. The author has put forward the concepts of four kinds of grades and the methods to determine them. They are respectively named cut-off grade, marginal grade, economic grade and the average grade of an ore deposit Ore bodies, Sub-marginal economic resources, marginal economic reserves and economic reserves can be contoured respectively with the former three.The value of investment for an ore deposit can be judged with the last one.