Abstract: The enhanced geothermal system is defined as engineering reservoirs that have been created to economically extract heat for electric power production at depth ranging from 3 to 10 km. As an important field of current geothermal development, the research is of interest to many developed countries, but China is still in its infancy. During the EGS operation, the design and operation of the fractured system are influenced by thermal-hydrologic-mechanical-chemical processes. This paper presents a brief analysis of the above four fields in EGS. The basic two-field coupling (T-H) is examined and the importance of T-H-M and the insignificance of T-H-M-C coupling are discussed. Related research progresses in numerical simulation are also introduced.