Abstract: The feasibility of ultrasonic welding process on carbon fiber reinforced polyphenylene sulfide (C_f/PPS) composites with thermal radiant preheating was investigated. The effect of preheating temperature and welding pressure on the formation of bonding interface and the mechanical strength of welded joint was focused on. It was shown that increasing preheating temperature improved the fusion of the resin at the bonding interface and 100% of bonding area was achieved with a preheating temperature of 110 ℃.The bonding area increased with the welding pressure and it reached 100% when the welding pressure exceeded 3 bars. The strength of the welded joint was enhanced with the welding pressure, but it declined at a welding pressure beyond 3 bars. The welded joint had a maximum strength of 20 MPa at a preheating temperature of 110 ℃ with a welding pressure of 3 bar.