Abstract: Geothermal energy, as a safe, stable and low-cost clean power resource, has been highly recommended in recent years. Geothermal system, the basic unit for the study of geothermal genesis, can be divided into 2 types including heat conduction and heat convection, and further subdivided into 5 subtypes of sedimentary basin, geopressure, dry hot rock, magmatic intrusion and deep circulation in terms of geological environment and heat transfer mode. This paper reviews the concept and research history of geothermal system, and discusses the main controlling factors and heat transfer mechanism of the two types of geothermal system.