Abstract: The welding wire of ϕ1.2 mm is usually used to welding hydraulic support structures. However, the low efficiency is hardly to meet the robot welding. The weld appearance, mechanical properties and welding efficiency of the robot welding with the welding wire of ϕ1. 6 mm were studied at the different welding parameter. The experimental results show that the welding seams have good appearance, less spatter, and the high mechanical properties at the welding current of 380～460 A. In addition, the weld seams by the current in 420～440 A have the best mechanical properties, and the welding efficiency is 48% higher than that with the welding wire of ϕ1.2 mm at the welding current of 440 A.