Since the 21st century, the third generation of wide band gap (Eg>2.3 eV) semiconductor materials represented by gallium nitride (GaN) and zinc oxide (ZnO) are becoming the core supporting materials for the development of semiconductor industry. Due to the difficult growth and high cost of GaN and ZnO single crystal, epitaxial technology is always used to grow GaN and ZnO films on the substrate materials. It is crucial to find an ideal substrate material for the development of third generation semiconductor. Compared with traditional substrate materials, such as sapphire, 6H-SiC, and GaAs, scandium magnesium aluminate (ScAlMgO4) crystal, as a new self-peeling substrate material, has attracted much attention because of its smaller lattice mismatch (mismatch rate is ~1.4 % and ~0.09 %, respectively) and suitable thermal expansion coefficient with GaN and ZnO. In this paper, based on the structure of ScAlMgO4 crystal, the unique trigonal bipyramid coordination and natural superlattice structure are introduced in detail, which is the structural basis of its thermal and electrical properties. In addition, the layered structure of ScAlMgO4 crystal along the caxis makes it self-peeling, which greatly reduces its preparation cost and has a good application prospect in the preparation of self-supported GaN films. However, the raw material of ScAlMgO4 is difficult to synthesize, and the crystalgrowth method is single, mainly the czochralski method (Cz), and growing techniques lag far behind Japan. Therefore, it is urgent to develop a new growth method of growing high quality and large size ScAlMgO4 crystals to break the technical barriers.