Abstract: The paper introduced the use of magnesite, dolomite, brucite, serpentine brine and magnesium salt as raw materials to produce magnesium oxide by different process routes and technologies. The methods for preparing magnesium oxide were classified, summarized and reviewed to identify their reaction mechanisms, advantages and disadvantages. Moreover, since nano-magnesium oxide has special characteristics, its preparation methods were also summarized, whose reaction mechanisms, advantages and disadvantages were explained. Finally, according to the current situation of producing special magnesium oxide (silicon steel grade and electrical grade magnesium oxide) in China, this paper pointed out its current production problems and discussed its future development.