Abstract: Vacuum diffusion bonding with different process parameters was conducted on 6061-T6 aluminum alloy after removing surface oxide films by chemical cleaning. Effects of bonding temperatures (500-560℃), bonding pressures (1.0-5.0 MPa) and holding times (0.5-3 h) on the interface morphology and shear strength of the welded joint were studied, and the optimal process parameters were determined. The results show that with the increase of the bonding temperature, bonding pressure and holding time, the weld seam of the joint became narrow and finally disappeared; the shear strength and welding rate were improved. However, when the holding time was extended to 3 h, the grains near the weld seam became coarse, leading to the decrease in the shear strength, and the joint had large deformation. The shear fracture modes of the joints with different process parameters were all brittle fracture. The optimal process parameters for the vacuum diffusion bonding were listed as follows:bonding temperature of 540℃, holding time of 2 h, and bonding pressure of 4.0 MPa.