The structure of melt is very important for the growth of high-quality large-size functional oxides, which are such materials widely used in military, high-tech manufacturing, and medical treatment. The structures for three typical functional oxide melts, such as oxide alumina, yttrium aluminum garnet, and lithium niobate have been reviewed in this paper. Several coordination units formed by cations and anions exist in each melt, and the coordination number, bond length, spatial structure and the percentage of various coordination units in the melts are obviously different from those in the corresponding crystals. The properties of these structure units are dependent on temperature. The coordination units connected with each other by the nodes. Both the cations and anions in the melts can be acted as nodes to connect the coordination units (polyhedron) in the melts. Phase transition is the kinetic process of melt structure transformation. Therefore, in addition to the melt structure, revealing the melt structure evolution kinetic process will help to understand the growth mechanism of large-sized crystals from a deep level.