Abstract: Wire and arc additive manufacturing (WAAM) is suitable for the integrated formation of large and complex structural components. To further increase the deposition rate of high-nitrogen steel wire while ensuring performance and reducing manufacturing costs, it is necessary to study the process characteristics of different diameter high-nitrogen steel wires in plasma arc additive manufacturing. This article investigates the melting characteristics and spattering process of HNS6-N5 high-nitrogen steel wire in plasma arc additive manufacturing, such as the influence of wire feed height and wire feed speed on spattering behavior and the variation of nitrogen element content in the weld bead. The results show that the wire feed speed and wire feed height determine the transition mode of high-nitrogen steel droplets and also affect the weld formation and process stability. Under the same heat input, spattering increases with the increase of wire feed height, while the nitrogen element content in the weld bead shows a decreasing trend. With the increase of wire feed speed, the nitrogen element content in the weld bead gradually increases. By adjusting the wire diameter, wire feed speed, and wire feed height, a stable process, low spattering, high nitrogen content in the weld bead, and high deposition efficiency can be achieved.