Abstract: The variations of arc pressure and weld characteristics in the welding of 2219,2A14 and 5A06 aluminum alloys were investigated based on the hybrid ultrahigh frequency pulse current variable polarity gas tungsten arc welding (HPVPGTAW) process. The experimental results show that compared with the conventional VP-GTAW (variable polarity gas tungsten arc welding) process,arc pressure and weld penetration expressed by the ratio of weld depth to width are enhanced predominantly with the effect of high frequency pulse current. Mechanical properties of welded joints are improved obviously. At the given pulse current amplitude and pulse duty cycle,the welding process is influenced significantly by the pulse current frequency in the range of 10 kHz to 80 kHz. At the given pulse frequency of 40 kHz,arc pressure and weld penetration of welded joints increased by about 90% and 70%,respectively,compared with that of welded joints with no effect of pulse current.