As many ore minerals host considerable amount of Re and Os, the Re-Os isotope system can be applied directly to study the ore-forming processes, including the timing and the source of metals. In addition, due to the different behavior during the crust-mantle fractionation, the Re-Os isotope between mantle and crust developed large contrast which makes it sensitive to trace the interaction between mantle and crustal derived materials. This isotope system has been widely utilized to study a large variation of mineral deposits including diamond, mafic-ultramafic igneous rocks related sulfide and oxide, porphyry, VMS, orogenic gold, and black shale hosted deposits. In the lecture, the principles of the Re-Os isotope system and its application in the study of economic geology will be introduced. The advantage and disadvantage of different minerals, and the recent development of analytical techniques and their challenge will also be covered.