The present work proposes a novel plasma cutting system using the ultrasonic frequency pulsed arc, and then experimentally investigates the effect of pulse process parameters on cut quality in the frequencies of 20-60 kHz. It is shown that kerf widths, bevel angle, straightness and dross attached level decrease obviously with the appropriate increases in the frequency and amplitude of pulse current. Furthermore, cutting heat affected zone narrows and cut hardness drops clearly in the pulsed cutting. This current pulsation can thus improve plasma cut quality remarkably, and finally leads to a narrower, flatter and more perpendicular cut of better remachinability. Experimental results simultaneously demonstrate that the effectiveness of the ultrasonic-frequency pulsed cutting process developed at the low current of arc.