Powder mixtures of CaO, ZrO2, and Al2O3 in various ratios were hot pressed and then reacted with titanium at 1600°C/30 min in Ar to evaluate the suitable ceramic crucibles for titanium casting. The interfacial microstructures between titanium and ceramic composites were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and analytical transmission electron microscopy (TEM). In the hot pressing composites, the CaZrO3, c-ZrO2, CaAl2O4 and CaAl4O7 phases were existed when the sample contained 20% Al2O3. The amount of CaZrO3 phase was decreased with increasing Al2O3, but that of c-ZrO2 was in the opposite manner. In the original interface, Ti3Al5 were found in the samples containing more than 20 vol% Al2O3, and the amount of Ti3Al5 increased with increasing Al2O3. With increasing Al2O3 amount, the residual ZrO2 participated on the ceramic side away from interface. When the amount of Al2O3 in the composites was above 20 vol.%, a large amount of CaZrO3 was formed at the interface to form as a barrier layer and possible suppressed the diffusion of oxygen from ceramic to titanium.