Based on the cold metal transfer (CMT) technique, a deposited wall of AZ91 magnesium alloy was fabricated by weaving wire and arc additive manufacturing (WAAM), the shaping, microstructure, and mechanical properties of the sample with the weaving arc were characterized and discussed by compared with the sample without the weaving arc, and the effects of the weaving arc on grain refinement and property enhancement of the AZ91 component by CMT-WAAM process were investigated. After introducing the weaving arc, the effective rate of the deposited wall could be increased from 84.2% to 91.0%, and the temperature gradient of the molten pool could be reduced with an increase in constitutional undercooling. The equiaxed α-Mg grains became more equiaxial due to the dendrite remelting, and the β-Mg17Al12phases distributed uniformly induced by the forced convection after introducing the weaving arc. Compared to the deposited component fabricated by the CMT-WAAM process without the weaving arc, the average ultimate tensile strength and elongation of the component by weaving the CMT-WAAM process both increased. The weaving CMT-WAAM component showed isotropy and has better performance than the traditional cast AZ91 alloy.