Abstract: This paper presents several study results on research of MIG/MAG power inverter for robot arc welding, with emphasis on welding dynamics. For dip transfer, the welding process may be divided into arc striking period and welding period, and be controlled respectively according to its own speciality. In the arc striking period, the key is to fully develop the System response so that a sound arc ignition rate and a fast-established stable arc can be obtained, while in the welding period the important factors arc to stabilize the welding process and to depress the welding spatter by, say, complex static characteristics and electronic reactor. So the authors studied these problems in the aspects of the static characteristics selection, the improving of arc striking, the control of welding dynamics, etc. Results have been applied to the prototype of NZM-400 MIG/MAG robot welding System and also to NBC-400 semiautomatic MIG/MAG welding machine.