The nanocrystalline materials exhibit the microstructure with an average grain size smaller than 100nm, which is responsible for their unique properties. A high thermal stability is the key for the application of nanocrystalline materials. Hence, the grain growth of nanocrystalline materials has been the focus of intense research efforts in recent years. This article reviews the current status of research in this field. The microstructural characteristics of nanocrystalline materials have been introduced. The effects of solute atom, the second particle and internal strain on the thermal stability of nanocrystalline materials are discussed. The basic theoretical models in thermodynamics stabilization and kinetics stabilization are summarized.