Nickel-based superalloys GH3030 and GH4648 were joined using the B–Ni73CrSiB–40Ni–S brazing filler metal. The effects of varying brazing temperatures on the microstructure and mechanical properties of the GH3030/GH4648 brazed joints were systematically investigated. The hardness of the base material, along with the microscopic morphology, composition, and tensile strength of the joints, was analyzed. The results indicate that the use of B–Ni73CrSiB–40Ni–S brazing filler metal can achieve an effective connection between GH3030 and GH4648 brazing joints. The four elements—Cr, Si, Fe, and Ni— enhance the bonding between the brazing filler metal and the honeycomb structure. The brazing temperature significantly affects the microstructure and mechanical properties of the joint. When the brazing temperature is low, the fracture surface will exhibit plastic deformation. When the brazing temperature reaches 1080 ℃ , the fracture exhibits a notable ability for plastic deformation, and the tensile strength of the joint is at its peak during this phase. As the brazing temperature rises, the formation of brittle compounds increases, significantly diminishing the mechanical properties of the joint. The fracture morphology results indicate that two fracture modes were observed: quasi-cleavage fracture and a mixed mode of quasi-cleavage fracture with micropore aggregation fracture.