Abstract: A new plasma-MIG welding process using single power source is described in this paper.It uses one dropping characteristic arc welding power source to supply electricity to the plasma and the MIG arc at the same time.Current distribution and adjustment,voltage and potential relation between the plasma and the MIG arc,metal transfer and arc shape have been investigated.The results indicate that this is a new and simple plasma-MIG welding process,it is easy to be used in production.