The study explores the impact of varying Ni composition on the microstructure and phase change temperature of 22MnB5 hot-formed steel jointed through laser welding. Employing optical microscopy, tensile testing machines, and JMatPro software, it examines the weld joints created with filler wires of differing Ni content. The results showed that post heat treatment, the joints formed with low-Ni steel wire comprise a mix of martensite and delta-ferrite, attaining a tensile strength of 1357 MPa. Conversely, those created with high-Ni wire yield a fully martensitic microstructure following heat treatment, reaching a joint strength of 1516 MPa-equivalent to 92% strength coefficient. Notably, a higher Ni concentration in welding wire complicates the formation of δ-ferrite during solidification; however, it accelerates the generation rate of γ-austenite.