Abstract: The exploration to the mineral internal structure and microscopic properties becomes a reality with the development of quantum chemistry theory especially the density functional theory (DFT)being put forward and fully developed and the improvement of computing hardware.This paper introduces the DFT and elaborates its applications to the mineral surface, the mineral structure and the reagents in detail. The influence of the mineral surface microscopic properties, the mineral internal structure and the interaction relationship between reagent molecules and minerals on the microscopic properties is obtained by applying quantum chemistry calculation to the mineral surface, mineral structure and flotation reagent.DFT should be combined with specific experiment and spectroscopy methods to provide a solid and reliable theoretical basis to mineral processing.