The invention discloses an aluminum alloy pulse ultrasound and electric arc composite welding device and method. Based on ultrasound and electric arc composite welding, the device further comprises a current and voltage detection circuit, a DSP, a single chip microcomputer, a triode switch circuit and a drive circuit. The current and voltage detection circuit is connected with the output end of a matching circuit of an ultrasound generation system. The current and voltage detection circuit is connected with the DSP. The DSP is connected with the drive circuit. The single chip microcomputer is connected with the triode switch circuit. The triode switch circuit is connected with the drive circuit. The drive circuit is connected with a DC / AC full-bridge inversion circuit of the ultrasound generation system. According to the welding method, ultrasound is applied to conduct pulsing processing, and aluminum alloy pulse ultrasound and electric arc composite welding is achieved. The aluminum alloy pulse ultrasound and electric arc composite welding device and method have the advantages of ordinary ultrasound and electric arc composite welding, the electric arc stiffness can be improved, weld penetration is increased, grains are refined, the size of molten drops is reduced, transition frequency is increased, splashing is reduced, high-quality welding under a common welding environment is achieved, aluminum alloy welding pores, welding cracks and the like can be reduced effectively, the microstructure of weld metal is optimized, and the mechanical property of welding connectors is improved remarkably.