Abstract: The influence of pulse current parameters of ultrasonic frequency pulse gas tungsten arc welding process for stainless steel on the arc behavior was investigated.The experimental results show that the pulse current parameters could have significant impact on arc characteristics, profile, force and penetration of welds.With the frequency of pulse current increasing, arc plasma has a more obvious pinch effect.The surface depression of welding pool has been caused by the axial effect, of which axial electromagnetic force and plasma flow force are the main causes.As a result of the depression, the welds penetration would be increasing with the increasing of frequency.