Raman spectra of KTa1－xNbxO3(KTN) single crystal,its melt, and the solid-liquid boundary layer in the growing process at different temperatures were measured in-situ. The structure transformation in KTN crystal growth process was investigated. The results showed that the Ta/NbO3 entities came into solid-liquid boundary layer from KTN melt, and they were transformed to Ta/NbO6 octahedron entities. And the structure of Ta/NbO6 octahedron entity was just like that of KTN single cell. Regarding Ta/NbO6 octahedron as growth units, the growth habit of KTN crystal in which the (100), (1-00), (010) and (01-0) faces are easily revealed was discussed. The thickness of the growth solid-liquid boundary layer of KTN crystal was about 80—90 μm.