In order to investigate the effect of CMT arc characteristics on the microstructure and properties of alumi-num alloy additive manufacturing components,5A56 aluminum alloy was fabricated by arc additive manufacturing with three mode of CMT,CMT-VP and CMT-P respectively. The arc behavior and metal transfer during additive manufacturing were observed by high-speed camera and data acquisition system,the effect of arc characteristics on the microstructure and mechanical properties of aluminum alloy additive manufac-turing specimen was studied. The experimental results show that the CMT arc characteristics has an impact on the arc behavior and metal transfer,the arc behavior is changed in the period of electrode negative in CMT-VP arc,the negative polarity climbs to the wire and wraps the droplet,the heat of melting wire is increased accordingly. In the pulse period of CMT-P,the voltage and current are both in peak and the current peak value is high,resulting in large arc force,the metal transfer in droplet mode and molten pool oscillation. When the welding current and deposition speed are the same,the heat input of the arc is CMT-P>CMT>CMT-VP. The grain size of the deposited metal with lower linear energy of CMT-VP arc is the smallest and the microstructure distribution is more uniform,the deposited metal shows more excellent mechanical properties and the average hardness is the highest,reaching 86.01 HV,and the transverse and longitudinal tensile strength are the largest in CMT-VP,which is 344.68 MPa and 324.61 MPa respectively,and the elongation get to 30.33% and 21.04% respectively. CMT-P has the largest heat input,which can get to form coarse-grained structure and poor mechanical properties.