Abstract: Take the shale section from a shale gas well in Sichuan Basin for instance. The XRF-measured element content and XRD-measured mineral content are used to establish the math calculation method for transformation from elements to minerals. It can calculate seven kinds of mineral in the rock, including clay mineral (kaolinite, chlorite, montmorillonite and illite), quartzes, feldspar and calcite. The calculated value of mineral content is compatible with the actually-calculated value. In addition, the content of elements is used to divide three components of the rock – muddy, sandy and ashy matters. Use of sandy/(muddy + sandy + ashy) matter appraisal of brittleness of shale is of great reference to implement transformation of shale reservoir.