Abstract: Abstract：The paper discusses the methods and theories of mineral search at depth on the basis of the experience obtained by the authors in exploration of succession mineral resources in crisis-facing mines of important mineral resources in China and the practice of mineral search at depth in recent years. The authors think that geological research, applications of geophysical and geochemical exploration techniques and drilling and tunneling are three basic factors of mineral search at depth. Geological research is the basic condition, geophysical and chemical prospecting is the technical support condition and drilling and tunneling is the condition for realization. They constitute the basic technical line. The paper discusses in an all-round way the studies of the characteristics of geological processes, ore field structure and indications for ore-forming processes. The study of the characteristics of geological processes related to ore-forming processes is basic work for determining the idea of mineral search. These geological processes include deposition, magmatism, volcanism, metamorphism and integrated ore-forming geological processes. The study of ore field structure puts forward the sedimentary structure system, volcanic structure system, intrusive structure system, fault structure system, fold structure system, compound structure system and post-ore structure system, as well as their applications in mineral search at depth. The study of indications of ore-formation processes includes studies of the indications of ore-forming characteristics and indications of physical-chemical conditions of ore fluids. The authors also put forward the theoretical basis of geochemical barriers to ore hydrothermal fluids and their research methods and application in search of mineral resources at depth.