Abstract: Wire and arc additive manufacturing (WAAM) using high-nitrogen steel is suitable for the integrated forming of large and complex structural components. In order to improve the deposition rate of high-nitrogen steel wire while ensuring the performance of additively manufactured components, it is necessary to study the plasma arc additive manufacturing characteristics of different diameters of high-nitrogen steel wire. The melting characteristics and spatter process of HNS6-N5 high-nitrogen steel wire in plasma arc additive manufacturing were analyzed. The study investigated the spatter behavior and N element content in weld metal during the additive manufacturing of high-nitrogen steel by designing different wire feed heights and feed speeds. The results show that the wire feed speed and height determine the transitional mode of high-nitrogen steel droplets and also affect the weld bead formation and process stability. Under the same heat input, decreasing the wire feed speed results in more intense spatter behavior of the molten droplets, while the N element content in the weld bead decreases. Increasing the wire feed speed gradually increases the N element content in the weld bead. By comprehensively adjusting the wire diameter, feed speed, and feed height, a stable process with low spatter, high nitrogen content in the weld bead, and high deposition efficiency can be achieved.