Reliable diffusion bonding of TC4 alloy was achieved using Zr interlayer. The interfacial microstructure was characterized by scanning electron microscopy(SEM), energy dispersive spectrum analysis(EDS) and X-ray diffraction(XRD). Effects of joining parameters on the microsturcture and mechanical propertie s of the joints were investigated. The results indicated that (Ti,Zr) diffusion layer with uniform components transition was formed at the interface of the joint, in which consisted of a large amount of lath-like α′-Ti(titanium martensite). With the increase of bonding temperature and holding time, the thickness of the diffusion layer increased, and the shear strength of the joint increased until the maximum shear strength was reached and then decreased. The maximum shear strength was 190MPa when the joint was bonded at 800℃ for 40min under 5MPa.