Ti-46Al-8Nb alloy was heated to 1 650 ℃ in a BaZrO3/Al2O3 composite mould at different time. The microstructure and the dissolution of mould after contacting the alloy melt at different time were analyzed by optical microscopy, scanning electron microscopy, X-ray diffraction and inductively coupled plasma emission spectroscopy, respectively. The interfacial reaction between the alloy melt and the mould was investigated. The results show that the dissolution reaction of the mould in the alloy melt results in the different thicknesses of the erosion layer on the inner wall of the mould (i.e., 1510, 2476 μm and 3 574 μm) after the alloy is held for 30, 60 min and 120 min, respectively. The erosion mechanism of the melt on the mould follows a dynamic model controlled by the diffusion dissolution. The dissolution of mould refractory results in the increase of the contents of O, Zr, Y, and Si elements in the alloy as the holding time increases, further leading to the increase of the microhardness of the alloy. After solidification, an adhesion layer is formed on the alloy surface. Meanwhile, BaAl2O4 and Y4Al2O9 phases are formed in the erosion layer. Two typical inclusions, i.e., (Ti, Zr)5(Si, Al)3 and Y4Al2O9, are formed in the alloy, and their contents increase with the increase of holding time.