Abstract: The SiC_p/6061Al MMCs joints were produced by arc-ultrasonic plasma arc in-situ weld-alloying by argon-nitrogen mixture as plasma gases and Ti wire as filler composite,and the effect of arc-ultrasonic on the microstructures and mechanical properties of the joints was investigated.The results indicate that without arc-ultrasonic(conventional plasma arc welding(PAW)),new phase AlN is slender needle-like,Al₃Ti is bulky,and the new particles such as TiC and TiN distribute unevenly in weld.Because arc-ultrasonic can refine the new reinforced composites such as TiC and TiN significantly and improve their distribution,new phase Al₃Ti become smaller and less.The test results of mechanical property show that the maximum tensile strength of the welded joint gained with arc-ultrasonic is 225 MPa,raising about 7% compared with conventional PAW.