The transient liquid phase bonding (TLP) welding test of DD5 Ni-based single crystal superalloy was carried out under welding conditions of 1280 ℃, 12 h, 0.01 MPa using the self-developed TLP interlayer material. The microstructure and precipitates of the welded joint were analyzed using SEM and the thermodynamic software JMatPro. The results show that the thickness of the interlayer has a significant impact on the microstructure of the welded joint. When the thickness of the interlayer is 120 μm, the microstructure and composition of the weld and the base metal tend to be consistent, and no obvious brittle precipitates are formed; the γ′ phase in the weld zone and matrix are basically combined. When the thickness of the interlayer is 160 and 200 μm, the athermally solidified zone (ASZ) is composed of brittle phases such as sunflower-like eutectic structure, fishbone-like borides, and block carbides rich in Ta and Hf. After post weld heat treatment (PWHT), the γ′ square degree of weld zone is significantly improved, and the size is basically consistent with that in the substrate. The stress rupture test was conducted under the condition of 980 ℃, 248 MPa. When the thickness of the intermediate layer is 120 μm, the stress rupture life can reach 145.54 h. And the results show that as the thickness of the intermediate layer increases, the stress rupture life of the joint continues to decrease, and the fracture mode changes from ductile fracture to brittle fracture.