Abstract: Plasma arc welding of SiC_p 6061 composite has been studied as argon or argon-nitrogen mixture has been employed as plasma gas. According to the theoretical analysis of the mathematical characterization of particle distribution uniformity, the influence of plasma arc welding on the distribution uniformity of SiC particles in the composite has been examined. It is proposed that the distribution uniformity of SiC particles has changed significantly after plasma arc welding. In the welding region, the distribution uniformity of SiC particles has decreased while there are much less particles than before welding.However, the decrease as well as the aggregation of SiC particles can be somewhat restricted as argon-nitrogen mixture rather than pure argon has been employed as plasma gas.