Abstract: The SiC particles (SiC_P) reinforced Al composites of SiC_P/ZL101 and SiC_P/Al with 10vol% of SiC_P were welded using Cu inter-layer under argon atmosphere at 550℃ by transient liquid phase diffusion bonding(TLP). The microstructure, shear strength, surface morphology of shear fracture and fracture path of the welded joints were analyzed. The results show that the Cu inter-layer is useful for the wetting of interface between the inter-layer metal and matrix by eutectic reaction of Al-Si-Cu (524℃) and Al-Cu (548℃) at eutectic temperature in the cast Al (ZL101) and pure Al (Al) matrix. Although some particles are gathered in the welded joints of cast Al matrix, the Cu content of the ternary eutectic reaction of Al-Si-Cu is 26.7wt%, which is lower than that of the binary eutectic reaction of Al-Cu (33wt%). Therefore it causes less CuAl₂ phase without aggregation in the welded joints of SiC_P/ZL101, which results in higher shear strength for the welded joints. While the intermetallic compound of CuAl₂ phase remained in the welded joints has an important effect on the mechanical properties of the welded joints. The shear strength of the two composite joints are 85.4 MPa and 73 MPa, respectively.