Metal transfer phenomena and spatter generation in CO 2 arc welding with a solid wire were investigated, and a low spatter welding process using a high frequency pulse rectangular current was developed. The optimal conditions of high frequency pulse CO 2 arc welding were determined to be a peak current of 450-550 A and pulse frequency of 450-750 Hz. These high frequency pulse currents influenced the droplet oscillation due to resonance between the applied pulse frequency and the natural frequency of the droplet. A droplet was regularly transferred by 9-11 pulses, and the average interval of metal transfer was y16 ms, which was half of that in conventional CO 2 arc welding. The average droplet weight is 34 mg, showing a large reduction in comparison with that of the conventional method. As a result, the total spatter weight was reduced by 70% in comparison with the conventional method, and particularly large spatters more than 0?5 mm in diameter were reduced from 25 to 3 mg s 21 .