Abstract: Butt welding tests were carried out on Invar steel with thickness of 19 mm by multi-layer multi-pass welding and multi-layer weave bead welding,and power consumption and efficiency of these two processes were calculated and analyzed. By observing and measuring the microstructure and microhardness of Invar steel weldment,the quality of the welded joint with the two welding methods was compared. The results indicated that when connecting thick plate Invar steel,multi-layer weave bead welding had less welding time,higher efficiency,and lower power consumption due to its less welding passes than that of multi-layer and multi-pass welding. The interlayer remelting zone in multi-layer weave bead welding was well fused,while obvious incomplete fusion defects were observed in multi-layer multi-pass welded joints. The width of heat affected zone of multi-layer weave bead welding was much smaller than that of multi-layer multi-pass welding. The average grain size and microhardness of multi-layer weave bead welding were slightly larger than that of multi-layer multi-pass welding.