The interfacial reaction of composite SiCw/6061 Al in a welded joint and its influencing factors by laser welding has been investigated. Experimental results show that the interfacial reaction between the matrix Al and reinforcement SiC whisker in the weld is inevitable. The needle reactant Al4C3 is the main factor responsible for degradation in mechanical properties of the welded joint. The extent of the interfacial reaction increases with increase in the laser beam output power. On the basis of the experiment results, it is found that the optimum welding technique for the composite SiCw/6061 Al by laser beam is to minimize laser beam output power on the premise of penetrating the weld. A new method for welding of aluminium matrix composites by fusion welding is investigated.