The SD method is a new method for calculating mineral reserves and exam ining mineral reserves. The SD theory is based and developed on fraction dimensi on geometry. It mainly consists of the SD orebody fraction dimension theory and the structural geovariable theory, from which a series of SD elements, methods an d expressions are derived. The SD method can not only calculate the reserves of random blocks and those of changed industry indexes based on different survey phases and different costruction degrees, but also determine the credible degree of calculated reserves and the engineering control degree. The SD method has been successfully applied in some mines and has been formally affirmed and promoted throughout China.