Abstract: The Cu-Ti brazing filler metal system can maintain stable heat transfer between C_f/C composites and Haynes 230 alloy at the service temperature range of 600–900 ℃. However, the existing C_f/C-Haynes 230 brazed joints fabricated using the Cu-Ti brazing filler metal system still have the problems of insufficient heat transfer efficiency and weak mechanical properties. To further improve the thermal conductivity and service strength of C_f/C-Haynes 230 joints, a Mo-Cu alloy interlayer with high thermal conductivity and low thermal expansion coefficient was introduced into the brazing filler metal, constructing gradient thermal conduction channels and efficient heat transfer pathways. Through the sandwich-like Cu/Mo-Cu/Ti structural design, the dual goals of thermal stress regulation and heat transfer pathway optimization were achieved. The optimized C_f/C-Haynes 230 brazed joint exhibited a thermal conductivity of 33.1–37.2 W/(m·K) in the range of 600–900 ℃, which was an approximately 6% increase compared with the interlayer-free system. By alleviating interfacial residual stresses, the room-temperature shear strength of the joints increased from 21 MPa to 25.4 MPa. The Mo-Cu interlayer, by synergistically optimizing thermo-mechanical properties, provided a reliable joining solution for extreme-environment components in the thermal management system of thermonuclear fusion reactors.