Abstract: To resolve the main issues of wire arc additive manufacturing, including the unstable heat and mass transfer, strong arc coupling and poor formation etc., a double-pulsed tungsten inert gas (TIG) with stepped filling wire additive manufacturing method was proposed. A series of deposited straight wall experiments with variable parameters were carried out. The image and thermal data of the droplet and weld pool surface were sampled simultaneously during the deposition process. The influence of wire feeding mode on the welding wire melting, droplet transition and molten pool behavior as well as the causes of the influence on the forming accuracy were analyzed in detail. The results show that the droplet transfer mode is the liquid bridge transfer in both the rear and lead wire feeding modes. Compared with the lead wire feeding process, in the rear wire feeding condition, the wire melting efficiency increases, the droplet transfer size decreases, the change of the molten pool height and width decreases, and the thermal stability is enhanced.The volume of molten pool is slightly increased by high-frequency pulsed arc. The straight wall deposition parts with high forming accuracy are obtained finally.