Gallium nitride (GaN) is a typical material of the third generation of semiconductor materials. It is an ideal material for application in optoelectronic devices and power electronic devices, due to its good physical and chemical properties and thermal stability. Fabrication of GaNbased devices on GaN single crystal substrates by using homoepitaxial technique is the fundamental way to obtain devices with high performances. This article reviews the research progress of method for grown of GaN single crystal substrate, such as hydride vapor phase epitaxy technology, trihalide vapor phase epitaxy technology, ammonothermal method and Naflux method. The future development of technology for mass production of freestanding GaN substrate is also discussed.