Abstract: This research focused on wire and arc additive manufacturing for mold material RMD545 and the experiment of single layer and single bead deposition forming technology was carried out. The forming characteristics were analyzed and the interval of good forming technology was determined. The multi-ayer single-bead deposition forming technology test was carried out with proper parameters and the surface was well formed without obvious defects. The microstructure and properties of single-layer single-bead and multi-layer single-bead were analyzed. The result showed that with the increase of depositing current, the cooling rate slowed down, the martensite transformation decreased and the bainite transformation increased in single-layer single-bead microstructure, which led to a lower hardness. During the multi-layer single-bead depositing process, different layer had different thermal processes. It made a microstructure variation along the height direction. Microstructures from bottom to top were tempered martensite + acicular ferrite + tiny amounts of bainite, martensite + bainite + tiny amounts of acicular ferrite, and lath martensite. The hardness ranged from 350 HV to 500 HV. The tensile test showed that mechanical properties of the additive manufacturing wall structure could meet the performance requirements of the mold repairing.