Abstract: Using plasma arc as heat source, the additive manufacturing of titanium alloy fuses layer by layer was carried out by AC assisted method. The influence of AC value on the microstructure and properties of the additive specimen was studied. The influence of the auxiliary AC value on the droplet size and droplet transition was observed by high-speed photography, the roughness of the stack morphology was measured, the structure and microhardness of the stack were observed, and the influence of the auxiliary AC value on the compression performance of the stack was analyzed. The results show that a more obvious AC arc will be formed and the plasma arc will swing, which will oscillate the molten pool. The surface roughness and grain size of the additive specimen are improved, and the grain size decreases with the increase of the applied auxiliary AC. When no AC is added to the AC value of 30 A, the grain size is reduced by 43.4%. At the same time, the addition of auxiliary AC can significantly improve the hardness and plasticity of the additive specimen. When the external auxiliary AC is 30 A, the hardness is 454.15 HV, and the compression strain is 0.280%. Without AC, the hardness is 406.45 HV and the compressive strain is 0.110%, which is increased by 2.5 times.