SiC particle (SiCp)/Al composite materials were fabricated via powder packed resistance seam welding additive manufacturing. The influence of welding speed on microstructure and mechanical properties of the specimen was investigated, elucidating the formation and fracture mechanism of single-pass multi-layer deposition. The results demonstrate that a dense internal structure of the specimen characterized by uniformly dispersed SiCp embedded within the Al matrix is formed. However, particle agglomeration and porosity defects are observed. The porosity increases with the increase in welding speed, and the microstructure of the RSAM-24 specimen has the highest density, characterized by a density of 2.706 g/cm³ and a porosity of 1.672%. The mechanical properties of the specimens decrease as the welding speed increases. Optimal mechanical properties are obtained when the welding speed is set as 24 cm/min. Specifically, the average hardness, tensile strength and elongation values are 463.736 MPa, 52.16 MPa and 2.2%, respectively. The tensile specimens predominantly exhibit fracture along the interlayer bonding interface and the interface between the Al matrix and SiC particles, and the damage mode is ductile fracture.