Abstract: A novel ultrafast-convert intermediate and high-frequency variable polarity arc welding technology for aluminum alloys was developed.The effect of variable polarity current frequency on the microstructure and mechanical properties of 2219-T87 weld joints was researched based on the variable polarity TIG welding process.The experimental results show that the structure in the weld zone is predominantly columnar in the case of lower variable polarity current frequency.The grain structures in the weld zone become finer and more equiaxed with the increase of current frequency.Tensile strength and percentage elongation of the weld joints also improve predominantly.The type of weld fracture is changed from brittle to the mixture of dimple and brittle.Under the current frequency of 1 kHz,the rates of weld tensile strength and percentage elongation of the joints are 69% and 58% than those of the base metal respectively.