For the CMT wire arc additive manufacturing of AZ80 magnesium alloy,the influence of different deposition currents on the forming characteristics of magnesium alloy samples was studied. The results show that the single-pass magnesium alloy samples with good shaping can be obtained by CMT wire arc additive manufacturing with a deposition speed of 10 mm/s and the deposition current of 85～125 A. The height of the middle stable region is slightly higher than that of the arc starting and arc ending points. And the height deviation is controlled within 2.6 mm. With the deposition current increasing from 85 A to 125 A,the height of the deposited layer decreases from 2.39 mm to 2.16 mm,while the width of the deposited layer increases from 8.61 mm to 14.23 mm. Too large or too small deposition current will affect the surface roughness of the samples. The minimum surface roughness is 0.16 mm when the deposition current is 105 A.