Direct diffusion bonding of hydrogenated TC4 alloy to Al2O3 ceramic was achieved. The typical interfacial microstructure of TC4/Al2O3 joint was TC4/α-Ti/Ti3Al + Al2TiO5/Al2O3, which was confirmed by means of OM, SEM coupled with EDS and XRD. The effect of the bonding temperature on the microstructure of joints was investigated. Results show that the phase constitution of reaction layers dose not change when the bonding temperature is changed. However, with an increase of the diffusion temperature, the thickness of each reaction layer increases. The activation energy of Ti3Al + Al2TiO5 layer are 213, 172 and 152 kJ/mol, respectively when the hydrogen contents are 0 wt%, 0.3 wt% and 0.4 wt%. The maximum shear strength of the joint reaches 128 MPa when the bonding temperature is 840 °C for 90 min and the hydrogen content in TC4 is 0.4 wt%. Moreover, fracture analysis shows that fracture occurs in the Al2O3 base metal side