Abstract: The influences of Ti-Al-Si-Mg and its oxides on microstructures and mechanical properties of SiC_p/Al MMCs joints welded by plasma arc in-suit welding were investigated,in which argon-nitrogen mixture was used as plasma gases and Ti-Al-Si-Mg flux-cored wire as filled composites.The results show that the formation of needle-like harmful phases Al₄C₃ is effectively inhibited by adding Ti-Al-Si-Mg flux-cored wire as filler.The fluidity and wettability of molten pool is improved and the stable molten pool is obtained.The mechanical properties of welded joint are effectively enhanced by the compact-grain structure and the new reinforced composites such as TiN,AlN,TiC,MgAl₂O₄ and fine grain Al₃Ti.The test results of mechanical properties show that the maximum tensile strength of welded joint with Ti-Al-Si-Mg flux-cored wire as filled composite reach up to 267 MPa.