Abstract: A kind of digital arc power supply for welding of aluminum-magnesium alloy was developed in this paper.Its control system and human-computer intercommunion system based on DSP and ARM were set up,and the digital welding-machine system and the double-pulse control process were analyzed.Through a lot of technical experiments on large step calibration,the expert database in the digital double-pulse welding of aluminum was constructed made to be laconic and modularized.Welding tests on aluminum in rectangular and trapezoidal double-pulse wave were conducted at different currents.From the welding wave shapes and welding seam forms,it can be seen welding current waveforms are regular and stable,which were without any phenomena of breaking arc,basically without any splashes.And welding beads are beautiful with clear fish scale.Adjustment on the modulated frequency in low frequency to change the width of fish scales helped achieve the preset form required.